The short answer: it depends, but we can give you these rough guidelines:

• For a TV, decoder, basic computer, a light, WiFi, a 600W desktop or trolley type inverter will be sufficient
• For a TV, decoder, more advanced computer or 2 normal ones, a few lights, WiFi, you will need a 1000W desktop, trolley type or wall-mount inverter
• For a TV, decoder, all lights in a 2-3 bedroom house, a few computers, WiFi, we recommend at least a 2kW wall-mount inverter
• For a TV, decoder, all lights in a 2-3 bedroom house, a few computers, WiFi, and a small aircon we recommend at least a 3kW wall-mount inverter
• For a TV, decoder, all lights in a 3-4 bedroom house, a few computers, WiFi, small aircon and to be able to boil the kettle or run the dishwasher occasionally we recommend at least a 5kW wall-mount inverter
• In order to take a 3-4 bedroom house completely off-grid, you will require at least a 7.2kW inverter
• In order to take a large house completely off-grid, you will require at least a 10kW inverter

For accurate recommendations, please book a more detailed assessment or system design on our “Services” page

We recommend having enough battery capacity to run your inverter at least for 1 hour at its nominal capacity. This means with an average half-load usage during Loadshedding, you will at least be able to get through 2hours.  Thus for a 3kW inverter you will need at least 3kWh worth of battery storage, for a 5kW inverter you will need 5kWh battery storage, etc, etc.

Most batteries are rated at least at 1C nowadays, which means it can discharge its full capacity in 1 hour. This allows a 5kWh battery to discharge quickly enough to supply a 5kW Inverter at full load, continuously.

Some batteries such as Pylontech are only rated 0.5C, which means it can only discharge half of its capacity in 1 hour, thus a 4.8kWh Pylontech UP 5000 battery, can only discharge at 2.5kW, so the rating of your entire system will only be 2.5kW. You will require 2 of these batteries for the system to function at its intended rating, and to ensure your warranties remain valid. The advantage of a lower charging and discharging current, is improved lifetime.

The figures vary slightly from one brand to the next, but in general the lifecycle cost of a Lithium battery is 40% cheaper than that of a normal Lead Acid type deep-cycle battery (including Flooded, Gel and AGM types).

The typical lifetime of a Lead Acid based battery is around 500 cycles. At one charge-discharge cycle per day, that’s about 1.5 years.

A Lithium battery is usually also designed for at least 2000 cycles, with some warranties extending to 6000 hours. Realistically, if you don’t over-discharge your batteries and your charging current is kept reasonable, 4000 cycles is very achievable on almost all models. At one charge-discharge cycle per day, this is almost 10 years!

A Lithium battery can also discharge much deeper than Lead Acid Batteries, with the exception of AGM’s which can discharge 75%.  A Lithium battery is typically specced to discharge 80 -95%, depending on the brand, thus most of the storage capacity is usable. A Flooded Lead Acid deep-cycle battery can only discharge 50% without being damaged, thus a 12V 100Ah battery has a theoretical storage capacity of 1.2kWh, but only 600Wh of this is usable. On a 12V 100Ah Lithium battery, you can use around 1kWh, which is almost double the usable energy.

If you only want backup for Loadshedding, a Lead Acid battery is probably OK, but then we would recommend AGM instead of Flooded or Gel (by the way: AGM and Gel is NOT the same thing). If you are planning on running solar now or in future, Lithium is the way to go since solar might give a few cycles per day and a Lead Acid battery might not even last 1 year.

We get this question very often, so we will first clarify which inverter does what, before making recommendations:

Grid-Tied Inverter:

• A true Grid-tied inverter is connected to the grid (municipal or Eskom direct)
• It has an integrated MPPT (or at least a PWM) Solar controller
• While solar energy is available, it will supply electricity to the connected loads on your premises.
• If the loads are higher than the solar can supply, it will supplement with electricity from the Grid (usually adjustable setting).
• If excess solar power is available, it will export it back into the grid (unless export blocking is enabled)
• In some cases, if the laws allow, exported electricity may be bought from the person owning the grid-tied inverter
• It does not have the ability to store energy in batteries or use energy from a battery

“What is the point?”, you may ask. Well in places where the grid is stable and has excess generation capacity (not South Africa), premises with these inverters basically use the Grid as their battery – storing excess solar power by day, and importing it at night.

In South Africa, this is clearly not a practical option, except for solar farms and a few other large commercial self-consumption solar producers. Grid-tied inverters are subject to heavy pre and post installation regulations from municipalities due to their direct, 2-way interaction with the grid. If you consider one, please ensure it is on the City of Cape Town’s approved inverter list, as the rest of South Africa is now starting to follow suit on the regulations and approved inverter list.  At Solar Spot you can be assured that we will never sell a Grid-tied inverter which has not been approved by the municipality.

Off-Grid Inverter:

• Contrary to the popular misconception, most Off-grid inverters can take a Grid (municipal or Eskom direct) input, bypass it to the loads and charge the batteries. Sometimes these are called “Hybrid Off-Grid Inverters” but that just causes unnecessary confusion. We will discuss true Hybrid inverters shortly.
• Most Off-grid inverters have integrated MPPT solar charge controllers. A few specialist, completely off-grid units such as the Victron Phoenix range, can communicate with an external, separate MPPT charge controller such as the SmartSolar.
• While solar energy is available, it will supply electricity to the connected loads on your premises. It will also charge the batteries with excess solar energy. These proportions are usually adjustable
• If the loads are higher than the solar can supply, or not enough solar power is available to charge the batteries, it will supplement with electricity from the Grid (usually adjustable setting).
• It does not have the ability to export back to the grid, unless it is connected completely incorrectly, which will cause serious failure and dangerous conditions. Municipalities may still require export-blocking devices to be installed for extra safety (see our SSEG section)

Due to its ability to store Grid or solar energy in batteries, its relatively low costs, and slacker municipal regulations, it is by far the most popular and practical inverter type for use against loadshedding and/or solar self-generation.

Please do not panic if your Off-grid inverter (or the one you are considering) is not on the Municipal Approved Inverters list. Since they are not designed to export to grid, the approval of the brand and model is not a requirement, but an export-blocking device might still be required for registration of your installation.

Hybrid Inverter:

• Many of our clients initially ask for a Hybrid inverter, while they are actually looking for an Off-Grid inverter with incoming Grid-connection
• True Hybrid Inverters are, as the name implies, a Hybrid between a Grid-tied inverter and an Off-Grid Inverter, featuring the strengths of both types
• It has an integrated MPPT (or at least a PWM) Solar controller
• While solar energy is available, it will supply electricity to the connected loads on your premises. It will also charge the batteries with excess solar energy. These proportions are usually adjustable
• If the loads are higher than the solar can supply, or not enough solar power is available to charge the batteries, it will supplement with electricity from the Grid (usually adjustable setting).
• If excess solar power is available, it will export it back into the grid (unless export blocking is enabled)
• In some cases, if the laws allow, exported electricity may be bought from the person owning the grid-tied inverter

Due to its multi-functionality, this type of inverter is still a very good solution for South African conditions, but they are usually considerably more expensive than an Off-grid inverter with the same capacity. However, since these are often “flagship” brands and models, they usually have a host of additional features, better build quality, longer warranties and better support. Thus, if your budget allows, it is still well worth considering a true Hybrid Inverter, such as our Deye and Sunsynk range.

If you are considering one, please ensure it is on the City of Cape Town’s approved inverter list, as the rest of South Africa is now starting to follow suit on the regulations and approved inverter list.  At Solar Spot you can be assured that we will never sell a true Hybrid inverter which has not been approved by the municipality.

This is a very difficult question we face daily, with MANY influencing factors. From our experience, taking into account a properly sized, designed and installed system (please read our section on “good Solar Designers” and “good Solar Installers), the forecasted increase in electricity prices, expected lifetime of quality equipment etc, it is realistic to expect a breakeven of 5-7 years.

If you purchase your Solar System outright, you will have a monthly saving on your electricity account, but in essence you have paid for it upfront. If you finance your solar system, your monthly repayments + interest might actually slightly exceed your current monthly electricity account. However, if electricity prices increase consistently at 10% year-on-year (which is roughly what NERSA allows Eskom currently), the compounding effect will mean that electricity prices will double in the space of 7 years.

Thus within 2-3 years you should start realizing a saving on your electricity account. After breaking even (having paid back your initial investment through savings on electricity) in 5-7 years, the electricity you then generate, is virtually free. If you have invested in good quality Solar Panels, Inverter and Batteries, it is possible to only start replacing certain equipment again in 10-12 years from initial installation.

Most of our clients invest in Solar systems for the convenience factor rather than only the predicted savings. If your ability to work and earn an income, or your daily routine is negatively impacted by loadshedding, then the actual value is of course considerably higher than the pure financial saving. Finally, it is worth remembering that an inverter fed from a battery will protect your equipment and appliances from the unplanned supply interruptions, resulting in another saving.

For a more detailed Return on Investment calculation, please order this from our “Services” page

2nd Life cells started their lives as Automotive grade cells in Electric Vehicle batteries.

As with all batteries, the capacity decreases with the number of usage cycles. After approximately 1500 cycles (4-5 years of driving), the cells have typically lost around 10% of their original storage capacity. In a vehicle it isn’t possible to just add 10% more cells, because of the weight and space constraints in a vehicle. However these cells usually still have 4500 cycles of life (or even more) left. These cells are then repurposed by building Energy Storage Systems for home, commercial and Industrial use. In these systems, it is easy to compensate for the lost capacity, by using a few more cells per battery, because space and weight is not such a massive factor.

Batteries manufactured from these 2nd Life cells, by reputable manufacturers such as Revov (who also build 1st life Batteries), are very good options for the cost-conscious consumer. These cells are tested and pass quality assurance processes before being repurposed, so it is not a cheap hand me down with unknown conditions. They still have full warranties and support, and the pricing is usually very competitive. Yes, their expected life is around 20-25% shorter than a 1st Life battery’s, but the purchase price is also 20-25% lower. In general the R/kWh/cycles is usually better on 2nd Life cells, so overall lifecycle cost is very competitive.

With Lithium and other scarce metals becoming more expensive and rare, 2nd Life cells will become ever more prevalent in future. It is an environmentally responsible option and a good solution to reuse electric vehicle cells.

The majority of Solar- and related equipment on the market today is very complex, technologically advanced and high-powered. Selecting equipment which is fit for purpose, and which can integrate with the other parts of the system, can be a complicated undertaking. Unfortunately there are many resellers and online stores who do not understand the equipment they are selling in sufficient detail. Conversely there are also many resellers and online stores who do have the requisite knowledge and experience. Here are a few key pointers to help you find the latter:

• Initial pricing is only one chapter of your solar story. Will you receive the back-up and support when you need it? If the reseller is relying on massive sales volumes at very low profit margins in order to make money, it is highly unlikely they afford to provide supporting resources to all clients who might need it
• If a supplier cannot advise you during the purchasing process, they will almost definitely not be able to assist you with any technical problems during installation and/or operation.
• Ask as many questions as you need to in order to be comfortable with your decision. A company which is contactable and can answer your questions, are more likely to be able to assist you with aftersales support.

Avoid purchasing single components spread across a multitude of suppliers. For example, if you are looking for the cheapest Lithium battery to pair with your new inverter, who is going to assist you when you have compatibility or setup issues? Neither the inverter nor the battery supplier might be willing or able to assist you. Purchase from a supplier who has experience in pairing products from within their comprehensive portfolio. If this is a first-time project, there is a very good chance that you might forget some key components in the system. If you purchase each major component form a different supplier, who will remind you to purchase the critical, smaller components? At SolarSpot we usually ask which equipment you will pair with the items you purchased from us, but we might not be able to resolve incompatibilities between our products and another supplier’s products retrospectively.

This section is applicable to equipment purchases and installation quotations alike. The following points will prepare you for assessing and comparing quotations

• Educate yourself on the basics, ie what types of inverters and batteries are available, so you are aware of what you are reading. This Section 1, and the following Section 2 will give you a good base to judge the advice an recommendations you receive from Installers
• Remember that as with most things in life, you get what you pay for, and that “penny-wise” is probably “pound-foolish”. Of course everyone has a budget, and we respect that, but then still compare items within the same ball-park.
• As mentioned previously, employing a Solar Designer is the most certain way to ensure the system will actually conform to your expectations. Freedom to get identical quotations
• Datasheets for all major equipment (Inverter, Solar Panels, Batteries) should be made available with your quotation, or available to download easily. At Solar Spot you will find Datasheets and other relevant documentation available for download directly below the Product Description
• Remember that not all items with the same terms in the Item headline specifications are created equal.

– Some 3kVA inverters have a true power output of 3kW, and some 3kVA inverters only have a 2.4kW output. The true 3kW machine will usually cost double the price of the 3kVA/2.4kW machine. The loss on the cheaper unit is not only on the input, but also on the continued expense of the lost energy which has to be paid for the inverter’s usable lifetime. Consider this carefully.

– Another example is two 5kWh Lithium batteries which might differ in price by up to 50%. This could be ascribed to many deeper specification differences such discharging current, charging current, predicted lifecycles, build quality, complexity of the BMS, etc

• When researching pricing, check the quoted price vs what other companies are charging for it, to determine the ball-park you should be operating in. If you only put 2 quotations with seemingly the same specifications, but not the same brands and models next to each other, you might be making a mistake. Even cheap circuit breakers used instead of expensive high-quality ones during installation, will have an impact on the price.
• Ensure you are receiving all the same protective devices from everyone who quoted. Protective devices and solar panel mounting hardware are the 2 lines where costs can often be saved in obscure ways, to the detriment of the client

 

 

• Good installation labour comes at a minimum price. Remember this, and feel free to ask the supplier to specify what level of staff will be performing the installation work. Also ask how many hours the installation will involve. Longer installation times often indicate a higher level of attention to detail, although experienced crews will work faster, but their hourly rate will also be significantly higher.

 

• If you are not happy with the pricing on the quotation, have an open discussion with the supplier. You would be surprised how often the alternative pricing you find on the internet is outdated, there’s no stock available, or, wait for it; the alternative price doesn’t yet include 15% VAT, whereas the quoted price does.

Solar Technology and Installations is a relatively new field when compared to orthodox electrical installation. So much so that even experts in the field usually learn something new every day. Because of this, the guidelines for installation is not nearly as well documented in SANS documents and other regulations, as we would find for other technical work. This means that a Solar Designer and/or Installer needs to be comfortable with calculating items from first principles, and also to apply experience and good scientific principles learned in other fields.

It is an unfortunate reality that many clients found out too late that they have gone down the wrong path, and we would like to save you from some of this expensive heartbreak. Below is a list of things to consider / assist you in looking for a Designer / Installer, and also to judge their capability beforehand using some of the tips in this section.

 

Solar Designers vs Solar Installers

A Solar Designer and a Solar Installer might be the same person or company, but it also might not. Although both professions are operating in the same field, there are some discreet but important differences and directions of specialization.

Some exceptionally good installers might not design the system to its optimum, so consider using a Solar Designer to design or at least verify the proposal for you. One example we see too often, is an incorrect number of solar panels, and an incorrect battery specification for the chosen inverter.

The money you spend upfront on a Solar Installer’s professional fees and a design report, is minimal compared to the money you will spend trying to fix an  incorrect system, or the losses due to sub-optimal performance of the system.

 

Solar Designer Deliverables

A Solar Designer must be able to confidently back up their recommendations with calculations, having taken into account:

• The user’s exact needs as expected upfront, but also fine-tuned through consultation
• System limitations
• Parameters and constraints of the equipment
• Impact of operating environment on the system

The deliverables of a Solar design, is a report which should indicate the following:

• Assumptions behind the design
• Specification of Inverter, batteries, solar panel and other associated equipment’s specifications and quantities according to which an installer or retailer can provide a detailed quotation. This enables an apples-with-apples comparison between different quotations
• Instructions for installation, ie wiring, solar panel orientation etc.

The Solar Designer should also offer a review of quotations, to ensure they meet the specified Design requirements

 

Qualifications

Be sure to ask for the Designer or Installer’s Qualifications and Background. There are many qualifications relevant to Solar Design and Installations:

• A SAPVIA approved qualification such as PV Greencard
• a Trade-tested Electrician
• a Registered Wireman
• Engineering Diploma or Degree
• Other formal Technical Qualifications / Occupations with a high level of technical detail
• Formal Working at Heights qualifications certified by the IWH,

are all good starting points.

Unfortunately a qualification alone does not guarantee proficiency in this field, so please consider the further points below.

 

Technical Knowledge and Confidence (a sign of experience)

Ask all the questions you need to satisfy yourself. Einstein famously said that if you cannot explain it simply, you do not understand it well enough. Thus, an installer who can explain the concepts and equipment to you confidently, most probably has a very good understanding and vast experience themselves. Ultimately you will have to operate your system, so it is important that the Installer can explain technical concepts in a way which is understandable to you as the end-user.

 

Layout and Content of Quotations / Proposals

A structured, detailed layout, with explanations is important. Datasheets for major equipment should preferably be provided.

NOTE: At Solar Spot you can find the Datasheets, User / Installer Manuals, Warranty Policies and other Technical Documents directly below the Product’s detailed Description (as underlined in red in the screenshot example below). These links are all redirected to a PDF file.

Beware of generalized quotations with little or no detail or logic. The following phrases are warning signs:

• “Installation”, as a one-liner with a massive amount of money next to it, with no indication of the hours it will take or who will be doing the work. It is impossible to determine if you are getting your money’s worth.
• “Installation Hardware” or “Mounting Equipment” as a one-liner with a massive amount of money next to it, with no indication of what this consists of. It is impossible for you as client to compare 2 quotes, apples-for-apples if you see this. Are you getting steel or aluminium solar mounting rails? What size cabling will be used? Connectors? Flashing? Fuses? Are you getting all the necessary protective devices (which if not included in their totality and according to the equipment manuals, your warranty might be void on most of the equipment)

* NOTE: A quotation must preferably be accompanied by an explanatory email or other communication which elaborates on the concepts and thought process followed when making the recommendations

 

Pricing

Pricing is of course an important factor for any client, but DO NOT make price your primary deciding factor!  You can lose a lot more money on a poor installation, or poor equipment supplied, than the additional upfront cost of using a good installer. If the equipment is of a different brand than the mainstream brands you see on the internet and on other quotes, and is considerably cheaper, please ask yourself why? The same applies to installation labour and material prices.

 

Safety

As the owner or person responsible for the premises, the client has a lot more legal liability than most people realise. This accountability cannot simply be passed on to a contractor. Ask the Installer about their Safe Working Procedures. Are they sufficiently prepared for working at heights, with live electricity etc? At Solar Spot we are experts in Industrial Safety, so ask us if you are unsure.

Once the installer is on site, observe their way of working. An installer should be taking the utmost care with your expensive equipment. A focus on the staff’s safety and their own tools and equipment, indicates a lot about an employer’s general approach to their attention to detail. It is an unfortunate statistical reality that unsafe work practices mixed with poor tool conditions, lead to unsafe and untidy end results.

 

Neatness

It’s an unfortunate reality (and almost a joke) that relatively inexpensive EGA ducting (trunking) and conduit has turned all installers into neat ones. We see pictures daily on Social Media posts depicting installations with lovely trunking, with everything looking neat, tidy and professional. But as the saying goes; don’t judge a book by it’s cover. What is really important, is what it looks like inside that trunking.

Ask your future installer to show or send you some pictures of while they are working and while the trunking is open.  An installer who is willing to show you the trunking open (and if it’s relatively neat inside while they are installing) is the installer you want. Real neatness is a sign of respect towards you as the client, your expensive equipment and the Regulations. Yes it is a working zone, not an operating theatre, so be realistic, but keep your eyes open.

 

General Control

We mentioned qualifications and experience earlier, but that means nothing if the persons performing the actual installation work are doing so unsupervised. The Electrical Regulations as well as the Construction Regulations which govern work at heights actually mention that General Control should be exercised during work. If the qualified person quickly drops off unsupervised staff in the morning and only quickly checks the progress for the day when the staff is picked up at the end of the day, General Control is not implemented. Work quality and compliance to regulations might be severely impacted by this lack of supervision.

 

Contactability and Support

A Leopard doesn’t change its spots – If a company do not answer their phones, do not return messages, and ignore your emails, while you’re still standing with your hard-earned money in your hand, do not expect their behaviour to change when they have your money and you actually require their support later on. They might be cheaper with their products, but it’s because they’re not putting anything else back into the business. Of course most of the installers and designers work long hours every day, so communication might be before or after normal office hours.

 

Initiative

Virtually every installation will hit a speedbump during installation. The number of unknowns are just too great to prevent every possible problem, especially since every building is built differently and is hiding some challenges. A good installer will definitely minimise these occurrences through good planning. However, a good installer will also be able to think outside the box and find a solution to dealing with problems if and when they appear.

During the quotation period, the client should be looking at the flexibility of the Installer and their ability to propose unique solutions to potential challenges, upfront. If no initiative is visible during the quotation phase, it is highly unlikely that any initiative will be taken to properly resolve problems encountered during installation.

• Be realistic and honest upfront about your expectations and your budget. There is a common misconception that revealing your budget, puts you in a vulnerable position where suppliers and installers will try to max out the budget and swindle clients out of their money. Quite the opposite is often true: good designers and installers will have respect for the client’s budget and can provide a much better value-for-money proposition if they know upfront what the boundaries are.
• An experienced Solar Designer or Installer will be able to provide the client with a rough estimate of a typical system, based on the client’s initial expectations. Consider this ball-park figure seriously, as it is highly unlikely that the actual price will be significantly lower. If this figure is beyond your budget expectations, be upfront so as not to waste any time or resources.
• Spend your money on those willing to spend their time on you. Someone who takes the time to give you detailed explanations and quotations, will most probably extend this attention to detail in their supply and installation work as well.
• To receive good service and build trust, be respectful with regards to companies’ intellectual property. Of course every client should do their due diligence, but do not just forward a detailed quotation from one installer to other installers who can just copy the design and try to undercut the price. A proper quotation is often also a design which was compiled with significant time and effort who can just copy the design and try to undercut the price. By doing this, a client will be shooting themselves in the foot, because an installer who cannot quote independently, will most probably not deliver a good installation service either.

Direct Current or “DC” is one directional flow of electricity. This is the type of electricity discharged by a battery. It is also the type of electricity generated by Solar Panels.

It is an easy type of electricity to generate and the only practical way to store it, but it is very inefficient to transfer over longer distances, require thicker cables and generates more heat.

Alternating Current or “AC” is a type of electricity which changes direction multiple times per second. This is the type of electricity we receive from Eskom, and therefore our houses and appliances are typically designed to use this type of electricity

It is a much more efficient type of electricity to transfer over long distances, at high voltages and low currents, thus the cables can be much smaller. It is the only practical way to distribute from power stations to the  end user, whether commercial, industrial or residential, and therefore forms the basic design input for appliances and equipment.

“Inverting” is the process of transforming the one-directional Direct Current generated by our Solar Panels or discharged from the battery, into Alternating current so our houses and appliances can utilise the energy in the way they were designed to do.

No, the types of electricity is so different, that appliances will be damaged severely and even create a very dangerous situation. DC usually operates at much lower voltages, and higher currents than AC, which will cause a very dangerous situation in our normal thin AC cables.  An inverter must be used!

Most modern inverters, combine additional functions into the unit, such as battery charger fed from either Solar Panels, AC supply from the grid, or both.

PV is an abbreviation for “Photo-Voltaic”, a combination of “photo” (the Greek word for light) and Volt (the driving force behind electricity flow). In essence the term Solar PV it describes exactly what it does; to generate electricity from sunlight.

This distinction is made because other Solar electric technologies exist, such as concentrated solar power (CSP), although these are typically used in large commercial installations.

Solar panels are manufactured from special silicon crystals. When light energy falls on these crystals, the electrons (sub-atomic particles which, as their name implies, form the basis for electricity), inside these crystals become excited and want to “escape”. This creates a Voltage, which means they are ready to flow as electricity. As soon as we close the circuit between the 2 opposite ends of the crystal, by attaching solar cables and a charge controller, a flow of electricity is established.

An MPPT is a type of Solar Controller which is very often incorporated into the inverter unit. MPPT stands for Maximum Power Point Tracking. In basic terms, it is constantly searching for the best combination of Voltage (the ability to drive electricity flow), and Current (the actual electricity flow) inside the solar panel.  As current starts flowing, the ability to drive more flow (Voltage), will start dropping. The power generated, is a combination of the Voltage and Current, so an optimum combination exists to extract the maximum power from the panel.

As the intensity and angle of the sun changes, so does this optimum combination. By throttling the current flowing from the panel, it indirectly controls the voltage in the system, and thereby attempts to ensure that the solar panel delivers the maximum possible power at all times.

The MPPT drops the voltage from the solar panels, to the optimum charging voltage of the batteries, while at the same time increasing the charging current to its optimum and safe level

A  PWM (Pulse Width Modulation) solar charge controller in essence uses quick on-off switching of current from the solar panels, to maintain a voltage just slightly higher than the actual battery voltage, and thereby pushing electric current into the battery to charge it. It is a basic, but effective and relatively inexpensive way to extract energy from a solar panel. However, it does not operate at the optimum conditions from the solar panel, nor the battery, and therefore it is inefficient.

This inefficiency is usually acceptable on small, mobile solar panels, but is not desired on large solar panel arrays which are expensive and thus the aim is to extract the maximum possible amount of electricity from it to be cost-effective in the long run.

Monocrystalline;

Monocrystalline panels are manufactured from thin slices of a single (“mono”) large crystal. This near-ideal crystal will have low reflection and refraction of the incoming sunlight, and this its conversion to electricity is very good. Efficiency is typically above 21%.

 

Polycrystalline;

Polycrystalline panels consist of many (“poly”) small crystals which are orientated randomly in the lattice. This random orientation is generally easier and less expensive to manufacture. Because PV crystals work best with sunlight shining perpendicularly onto the crystal, the randomly orientated crystals which refract and reflect some of the the incoming sunlight, will lead to some efficiency losses. Efficiency is typically below 18%

 

The image below indicates the clear colour difference between Monocrystalline and Polycrystalline panels, both manufactured by Canadian Solar. The blue hue of the Poly panel, is due to the many small crystals which are scattered randomly, vs the black single crystal construction of the Mono panel.

Impact of Cell Type on Solar Panel Efficiency:

As can be seen in the images above, a portion of the incoming sunlight’s energy is converted to electrical energy, but a significant part is reflected, refracted and converted to other forms of energy such as heat. When a solar panel’s power is rated, the amount of electricity which can be generated under Standard Testing Conditions at the Maximum Power Point, is measured against the total amount of incoming sunlight on the solar panel. The STC power available in sunlight is 1000W/m2.

As an example, consider a 540W JA Solar Monocrystalline panel which is approximately 2.2m long x 1.1m wide. This give a surface area of 2.42m2, which equates to 2420W available from the sunlight shining on this panel. The efficiency of this panel = actual output / available solar energy = 540W / 2420W = 22%.

 

Half-Cell Panels:

The cells in a half-cell panel are literally cut in half. The 2 half-cells are smaller and less prone to damage from vibration, bending stresses etc. This makes them an excellent choice for use in rugged applications such as camping and overland adventures. Their mechanical strength also makes them less prone to cracking in wind-loads, hail, etc.  The sum of the internal resistance of the 2 half-cells is lower than the internal resistance of a single full cell, and therefore the losses are slightly lower. This coupled with its ability to handle partial shading better, results in a slightly higher power output. JA Solar is an industry leader in half-cell panels, our selection can be viewed here:

https://www.solarspot.co.za/product-brand/ja-solar/

This image shows the Half-cells in a JA Solar mono panel:

 

Which Type of Panels should you purchase? Mono / Poly / full-cell / half-cell?

As can be seen in the images above, there is a lot more chaos present in the Poly panels and therefore the efficiency is undeniably lower.  However, the common misperception that Mono-crystalline panels’ higher efficiency will yield a better power output, is not entirely accurate. The efficiency was already accounted for when the panel’s output rating was determined. This means that in standard applications, a 455W Mono panel, whether full-cell or half-cell, should yield the same output as a 455W Poly panel.

It is however true that while the sun is at lower altitudes and thus a lower angle, the refraction and reflection on Poly panels will be proportionally even higher than on Mono panels, and thus the average output of a Poly Panel over the course of a year will be slightly lower. Add in some shading, and the half-cell panel starts to “shine”.  All panels of a certain crystal type is not created equally though, so the brand and quality of the panel is a very important factor. Canadian Solar for example, manufactures their Poly HiKu panels in a hybrid process close to that of Mono panels, and therefore can be superior in performance to many cheap Mono panels. Find our selection of Canadian Solar panels here:  https://www.solarspot.co.za/product-brand/canadian-solar/

Ultimately we recommend purchasing a well-known brand such as JA Solar or Canadian Solar, which both have excellent linear output lifetime performance forecasts and warranties, instead of over-focussing on the crystal and cell-types only.

STC:       Standard Testing Conditions for Solar Panels. This attempts to fix certain variables such as temperature, solar irradiance, refraction though the atmosphere etc, when testing solar panels, to allow a direct “apples-with-apples” comparison between different brands and models of panels. The most important factor here, is the cell Temperature of 25°C, as temperature is one of the biggest environmental impacts which could push your solar panels’ output into dangerous territory, and this has to be considered carefully when deciding how many panels to install.

Voc:       “Open Circuit Voltage” – The maximum voltage the Solar Panel can generate under Standard Testing Conditions.  This is probably the most important parameter, as it can be the most influential and/or damaging to your Solar Charger if calculated incorrectly. Measured in Volts [V]

Isc:         “Short Circuit Current” – The maximum electrical current the Solar Panel can generate under STC, if the cables are short-circuited, not flowing through a resistor or load.   Measured in Amps [A]

Vmpp:  The Solar Panel’s Voltage at the Maximum Power Point.   Measured in Volts [V]

Impp:    The Solar Panel’s Current at Maximum Power Point.   Measured in Amps [A]

MPP:     Maximum Powwer Point – the point at which the combination of Voltage and Current from the Solar Panel will generate the maximum amount of Power. In a very simplified form, there is a combination of Voltage and current which will yield the best possible Power output from the Solar Panel. The curve indicating Voltage vs Current, is constantly changing as the sunlight’s strength varies

The Voltage between the panel’s positive and negative wires have an inverse relationship: When a solar panel is placed in light (even on a cloudy day), a voltage will appear between the positive and negative pole. This means it is ready to start driving the flow of electricity. As soon as the poles are connected and current starts flowing, the voltage will start dropping. On a cloudy day the Voltage will drop so quickly that the panel basically loses its ability to drive the flow of electric current.

Since we determine the Output Power as the product of the Voltage and Current, there is a specific Power output for every Voltage and its associated current. We can indicate this Power Output as the area of a block which fits under the Voltage-Current Curves as indicated below.

 

There are many possible blocks representing the available power, which can fit under this graph. In the next graph, a high voltage and low current situation is shown. If each small yellow block represents a Power unit, the Panel would be generating 58 units with this combination of Voltage and Current.

A lower Voltage, higher Current condition will yield a different output, for example on this graph, 52 units will be generated:

 

Operating in the centre of the available Voltage and Current ranges, can also yield a good Power output, as can be seen in this graph:

 

As the curve representing this Voltage-Current relationship changes continuously, the MPPT solar charge controller’s function is to constantly search for this point where the Power output is maximised.

When solar panels are connected together in strings and ultimately into a solar panel array, the Voltage and Currents of the individual solar panels contribute to the system, but also impact each other.

Key features when connecting solar panels in series:

• “Series connection” is when the positive pole of a panel is connected to the negative pole of the next panel, and repeating this for all panels
• The total Voltage of the series string, is equal to the sum of the Voltage of the individual panels
• The total Electric Current (I) through the series strong, is identical through each individual panel, and is limited by the panel with the lowest possible current

Practical Implications of Solar Panels connected in Series:

• When Solar Panels are connected in series, their Voc’s and Vmpp’s are added together. This must be compared to the minimum, maximum and optimum voltages of the Solar Charger to ensure safe and efficient operation
• When Solar Panels are connected in series, their Isc’s and Impp’s are governed by the panel with the lowest current.

*Thus, if 1 panel in a series string is even partially shaded and cannot produce current, or is rated lower than the other panels in the string, the current and by extension the power output of all panels in the string are affected negatively

When solar panels are connected together in strings and ultimately into a solar panel array, the Voltage and Currents of the individual solar panels contribute to the system, but also impact each other.

Key features when connecting solar panels in parallel:

• • “Parallel connection” is when the positive poles of all panels are connected together, while the negative poles of all panels are connected together.
  • All Voltages in the parallel array are equal
  • The total Electric Current (I) through the series strong, is equal to the sum of the currents through each individual panel

Practical Implications of Solar Panels connected in Parallel:

• When Solar Panels are connected in parallel, the Voc’s and Vmpp’s are equal
• When Solar Panels are connected in parallel, the Isc’s and Impp’s are added together. This must be compared to the maximum current specified for the Solar Charger to ensure safe and efficient operation

* Parallel connected panels or strings can generate very high currents. High currents are dangerous, require  thick cables and generates significant heat which lead to inefficiency. Therefore the majority of modern charge controllers are designed for high voltages and low currents

• As with most electronic and electric equipment, solar panels are affected negatively by an increase in the crystals’ temperatures, and therefore a cooler cell temperature will lead to higher Power Outputs, while a hotter cell temperature will lead to a drop in performance.
• Note that we mention cell temperature, not ambient temperature. Although the lower bounds of a cell’s temperature will very seldomly be below ambient temperature, the upper bounds of a cell’s temperature will almost always exceed the ambient temperature. Think of any dark surfaces left in the sunlight. Interestingly, the blue colour of Polycrystalline panels will usually run at a slightly lower temperature, and are thus less impacted by hot climates than the black Monocrystalline panels.

VERY IMPORTANT:  Temperatures lower than STC (25 degrees Celcius) will cause a significant increase in the Voc and Vmpp of panels, if otherwise good sunlight is present. This can push the Voc of a solar strings above the rated voltage of the charge controller of the panel array’s Voc was specified too close to the charge controllers maximum Voc. Charge controllers can be damaged permanently and catastrophically if the rated Voc is exceeded.

Conversely, high temperatures might drop the Voc below the charge controller’s startup voltage, and although this is not a dangerous situation such as over voltage, it is not ideal to lose out on otherwise good sunlight.

Types of Solar Cables

Only Cables specifically designed and specified for solar panel use should be installed with solar panels. Normal housewire or other AC rated cable, and even battery cable should not be used, because:

• DC currents behave very differently in Cables than AC, causing higher temperatures and losses
• Solar cables are often exposed to the elements such as sunlight which will degrade the insulation around normal cables
• Designated Solar Cable is insulated by 2 layers – a silicone sleeve which us temperature resistant and protects against kinks in the insulation and the copper strands, and an Abrasion and UV resistant insulating covering
• The strands in solar cable are individually plated to ensure maximum conductivity within the cable and the connection points

Specialised Solar Cables are available in out online store here: https://www.solarspot.co.za/product-category/cables/solar-cables/?product_brand=zonn-kbe

Solar Cable Sizing

Solar Cable sizing is a complex topic, as the Current through the panels, the Voltage across the panel, Length of Solar Cables, Temperature all play an important role. In order to simplify the process slightly, we have generated the Tables below for guidance. We have generated the Tables for the 2 most popular Solar Cable Sizes: 4mm^2 and 6mm^2. Use the Tables as follows:

1. Locate the Short Circuit Amps of the Solar string to be connected to the cable
2. Locate the Length of the planned cable run
3. Find the Voltage drop value where the Amps and Length intersect
4. Calculate the % drop of this Voltage drop value vs the Open Circuit Voltage of the string
5. The % Voltage drop should not exceed 1.5%
6. Select the size cable which is most suitable
7. If you have any difficulties or doubts, we can perform the design for you, make a booking on our “Services” tab

 

Various connectors are manufactured specifically for Solar Applications. Please do not use connectors or plugs which are not rated to handle the DC Voltages and Currents present and possible in the system.

SAFETY NOTES:

• Not all MC4 connector, even from the same manufacturer, will have the same ratings. This is specifically important when using splitters/ combiners where high DC currents will be present.
• DC connectors should never be connected under load! Use dedicated and purpose-designed DC circuit breakers to safely open the circuit
• Use certified electrically insulating gloves when handling connectors and solar panels
• As extra precaution, cover solar panels with a blanket or similar to de-energise the panel before connecting  connectors

 

MC4 Connectors

• These are the most prevalent connectors on Solar Panels, combiner boxes, inverters with dedicated MPPT connector inputs etc.
• MC4 connectors are equipped with O-rings to seal against water and dust ingress, and can be used safely outdoors
• Special crimping tools should be used to connect these connectors to Solar Cables, do not use Pliers!
• Only use reputable brands with certification, as many cheap imports are flooding the market and can cause severe and unnecessary danger

Find MC4 Connectors here:

www.solarspot.co.za/product/staubli-pv-kbt4-6ii-ur-female-solar-connector/

www.solarspot.co.za/product/staubli-pv-kst4-6ii-ur-male-solar-connector/

www.solarspot.co.za/product/staubli-pv-azs4-2-male-to-1-female-splitter/

www.solarspot.co.za/product/staubli-pv-azb4-1-male-to-2-female-splitter/

 

MC4 EVO 2 Connectors

• NOT COMPATIBLE WITH NORMAL MC4 CONNECTORS!
• MC4 EVO 2 connectors are becoming commonplace on higher powered solar panels , because if their ability to handle up to 1500Vdc, as can be found on commercial and industrial applications
• MC4 EVO 2 connectors are rated IP68 against water and dust, can handle many industrial chemicals such as Ammonia, and harsher environments including saltwater
• Special crimping tools should be used to connect these connectors to Solar Cables, do not use Pliers!
• Normal MC4 crimping tools cannot be used for MC4 EVO 2 connectors, or vice versa!
• Only use reputable brands with certification, as many cheap imports are flooding the market and can cause severe and unnecessary danger

Find MC4 EVO 2 Connectors here:

www.solarspot.co.za/product/staubli-pv-kst4-6ii-ur-female-solar-connector-evo2/

www.solarspot.co.za/product/staubli-pv-kst4-6ii-ur-male-solar-connector-evo2/

SAFETY NOTES:

Solar Cables are high-risk components of an installation because they:

• Are very often under high voltages (exceeding 50Vdc)
• Carry relatively large DC currents over long distances and can generate significant heat
• Are often exposed to many environmental factors such as moisture, chemicals, salt etc
• Can easily chafe on structures through which they are routed, losing their insulation properties
• Are often within reach of human touch
• Are often underestimated because they carry DC
• Are energised by solar panels which are switched on whenever there is sunlight, there’s no quick “off” switch
• They will conduct lightning down to earth

The following devices are important on any Solar Cabling installation:

 

DC Surge Arrester / Surge Protection Device (SPD)

• Every set of cables need to be protected by a DC Surge arrester. Without this, most manufacturers of inverter and/or solar charge controllers will not honour the warranty if DC overcurrent is suspected
• The DC Surge arrester must be of the Type 2, 2-pole type
• The Earth terminal must be earthed to an earth peg or earth mat of which the earth continuity has been confirmed, with a cable exceeding the size of the Solar Cables in use, to ensure that fault-currents are directed down to Earth
• We do not recommend earthing the Solar Cables’ earth to the AC DB’s earth, as it could redirect lightning induced energy directly into the AC DB
• PLEASE NOTE that Surge Arresters are on-time-use devices. When the flag is red, it has to be replace

DO NOT use an AC Surge Arrester on a DC application. DC specific Surge Arresters can be found here: https://www.solarspot.co.za/product-category/protection/dc-surge-protection/

 

Solar Fuses

Solar fuses are installed to:

• Protect the Solar Panels against over-current situations
• Protect the Solar Cables against over-current, over-temperature and short-circuit conditions
• Protect the Solar Charge Controller, whether standalone or integrated into an inverter, against over-current conditions

Location of Fuses

• Each Pole of of the Solar Cables should be protected by at least 1 fuse
• Fuses are typically installed in the dedicated Solar DB.  IMPORTANT: DC items such as Solar terminals may not be located in a DB with AC terminals!
• If there are long runs of cable with high currents, especially in parallel setups, and/or where the cables can arc against structures, without the DB-based protection having any protective function, an inline fuse close to the solar panels is highly recommended as additional protection

Specification of Fuses

• Fuses must be selected so as to protect the lowest rated component in the circuit.  For example: if the MC4 connectors are rated at 25A, the Solar Panels at 13A, Cables at 30A, Inverter’s MPPT at 18A, then the fuses must be sized so as to protect the Solar Panels.
• On Solar Panels, the maximum Fuse rating is usually Isc + 50%, however we recommend selecting the fuse considerably lower, ie Isc + 20%.
• Solar Fuses come in small size increments, so it is easy to select an appropriate size fuse for your installation. Our variety of Solar fuse-holders and fuses can be found here: https://www.solarspot.co.za/product-category/protection/solar-fuses/

 

DC Circuit Breakers

• A DC Circuit Breaker should be installed in the Solar Cable Circuit to allow easy disconnection of the circuit without arcing. Pulling a fuseholder open or pushing it closed while the panels are energised, will result in arcing.
• We do not recommend replacing Solar fuses with a DC Circuit Breaker, but instead to supplement it, by using both
• DC Circuit Breakers do not come in the same small size increments as Solar Fuses, and therefore it isn’t as simple to find a perfect match. The DC circuit breaker can be selected a few Amps larger than the Solar Fuses
• Our variety of Solar fuse-holders and fuses can be found here:  https://www.solarspot.co.za/product-category/protection/dc-circuit-breakers/

 

Solar Panel Earthing

Solar Panel frames must be earthed, the protective devices mentioned above will not necessarily protect against current leaking from a damaged solar panel into the frame and mounting hardware

It is important to not that the employer is accountable for safe work on a premises. This means that a owner of the premises needs to ensure that persons performing solar installations on the premises are:

1. Either fully competent to manage the risk themselves, and appoint them as such, or
2. Ensure that workers performing work directly for the owner, are informed about the dangers, trained and equipped to work in a safe way

Furthermore it is important to remember that the electrical installation on a premises, is the responsibility of the owner.

Remember, ignorance is not a defence in court, if your workers or contractors get injured or die while working on your premises, there will be serious civil and criminal investigations. The employer needs to be able to prove that all relevant control measures were in place.

Safety should always be managed according to the Hierarchy of Controls.

Electricity is a very hazardous form of energy, the amount of electric current required to power a 7 Watt LED lightbulb is enough to stop a human heart, or badly damage it. In addition to cardiac arrest, electric current or arc-flashing can also cause severe burns.  The electricity generated by an inverter is no less dangerous than the electricity provided by Eskom, especially if it not yet run trough protective devices such as Earth Leakage relays.

Mitigations for AC hazards:

1. Always assume installations to be electrically energized (alive). Bear in mind that any UPS system feeding to the DB, can energise the DB even if the Main Switch is switched off.
2. The neutral is even more dangerous than the live, as it can create a false sense of security. For this reason we recommend isolating switches to always be 2-pole (on single phase systems) or 4 pole (on 3-phase systems), to ensure no feedback current can flow via the neutral.
3. Always switch off the main switch from the grid, as well as the isolator feeding from the inverter.
4. Always use a voltmeter to test for any voltage present on the side of the isolator you are planning to work on
5. Do not assume that you are safe to work on the incoming grid connection when there is loadshedding, it can be switched on at any time, or your neighbour with an incorrectly installed generator or inverter could be energizing your system. Always isolate and always measure to be sure.
6. If you have to work on energized (electrically alive) systems, or on isolated systems where you do not control the isolator, use electrically insulating gloves which at least conform to the nominal voltage of the system, and certified according to an accredited standard such as: en 60903:2006(en 60903:2003 + ac2:2005).

Solar systems have 2 main sources of DC; the solar panels and the battery system. DC is often underestimated because items such as a 12V car battery can usually be touched without feeling anything. Don’t be fooled, DC can be very dangerous and because it doesn’t cycle like AC, once you touch it and your muscles start contracting, it is very difficult to let go.  DC also tends to generate more heat than AC.

In industry, 30Vdc is considered the danger threshold. Bear in mind that a 24V system can charge close to that level, so be careful. Also bear in mind, even a 12V battery, when short-circuited will generate a lot of arcing, a lot of heat, and a current easily exceeding 3000A !  Most modern solar panel arrays operate in the region of 500Vdc, with currents in the region of 15A, a dangerous combination for the human body

Mitigations for AC hazards:

1. Always assume installations to be electrically energized (alive). Remember that a Solar Panel in sunlight cannot be switched off, it will always be live. Many batteries also cannot be switched off.
2. Always use a 2-pole isolator, especially on solar panels where it is difficult to determine the source polarity
3. Always use a voltmeter to test for any voltage present on the side of the isolator you are planning to work on
4. Use electrically insulated gloves when handling solar panels or their cabling
5. If possible, cover solar panels with a blanket or similar when working on them, to ensure no sunlight can energise them
6. Earth solar panel frames
7. Before connecting solar panels to the array cabling, ensure the DC circuit breaker in the DB, as well as the fuseholders are open
8. Before connecting batteries, open the fuse disconnector. Fuse disconnectors must be opened closed quickly and firmly to prevent excessive arcing

While most owners of premises, and all Installers are aware of the electrical dangers involved with solar installations to a certain extent, the risk of working at height is often overlooked or completely ignored. Again, ignorance of the regulations is not a valid defence in court.  The following are very important points to consider:

1. Someone doesn’t have to fall far to get seriously injured or be killed, a stepladder is high enough. The idea that only double-story building or higher are a danger, is misplaced and incorrect. The definition of Working at Height is “anywhere where a person can fall off of, into, or over a structure”.
2. Just handing someone a harness, does not qualify as “making the workplace safe. On the contrary, using a harness incorrectly can sometimes even be more dangerous than no harness at all. Remember the hierarchy of controls require you to consider many other steps, with Personal Protective Equipment such as a harness being the very last, and least desired step.

Mitigations for Working at Height hazards (in sequence of the Hierarchy of controls):

1. Consider alternative positions for installation, where the risk of falling is reduced
2. Use physical barriers to prevent dangerous positions from being accessed
3. Provide the necessary training and use applicable documentation to manage risk
4. Ensure all workers have a valid medical certificate allowing them to work at heights
5. Provide the correct PPE for which the workers have been trained

Due to the complexity of working safely at heights, we recommend that any person who will work in a risky position, attends IWH accredited training. This includes everyone from general workers who install solar panels and cabling, to the supervisor in charge of ensuring safe work. We recommend Rope Access Inspection for all training.

 

 

 

Course info, contact information is available on their site and bookings can be made directly here:

https://www.rope-access.co.za/training/fall-arrest/fall-arrest-and-basic-rescue/

https://www.rope-access.co.za/training/fall-arrest/basic-fall-arrest/

The Occupational Health and Safety Act and its accompanying regulations are applicable to many aspects of Solar system installations. The Regulations of particular concern are listed below, but should not be read in isolation.

• Occupational Health & Safety Act
• Sections 8, 9, 11, 12, 16 are particularly noteworthy as they deal with the accountabilities and responsibilities of employers and clients

PDF:       Occupational-Health-&-Safety-Act-85-of-1993

• General Safety Regulations

PDF:       General-Safety-Regulations-1986

• Asbestos Regulations
• Especially important when working on roofs or wall sheets made of suspected Asbestos, and/or with insulation made of suspected Asbestos
• Higher probability in buildings constructed before 2002
• Illegal to drill into, cut or disturb suspected Asbestos

PDF:       Asbestos-Abatement-Regulations-2020

• Construction Regulations
• Of particular interest are the definitions of the “client” and a “competent person”
• Section 10: Fall Protection is very important to note for all solar panel installations on roofs

PDF:       Construction-Regulations-2014

• Electrical Installation Regulations
• Certificate of Compliance must be issued for all installations
• General Control must be exercised

PDF:       Electrical-Installation-Regulations-2009

• Electrical Machinery Regulations
• Specifically important is Section 4: Duties when working on disconnected electrical machinery, which is particularly applicable to work in inverters and other equipment not connected to an energy source

PDF:       Electrical-Machinery-Regulations-2011

Municipalities require registration for Solar Systems. This process is guided by various documents available below, or from    https://www.sseg.org.za/

Solar Spot is committed to assist authorities and clients to work towards a legally compliant co-generated grid.