How much will a solar power system cost for my home?

The cost of a solar power system depends on a number of factors, including your load requirements (i.e. how much power you need to run your appliances), the energy efficiency of your home (e.g. do you use energy efficient light bulbs?), and the electrical standards of your home. Once you have completed the enquiry form, we will arrange a site inspection in order to make an accurate assessment of your solar power requirements and provide you with a detailed quotation.

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But what about winter?

In actual fact, solar panels do not react well with heat and cooler panels produce more energy. The clear skies of South African winter days are optimal for solar power generation. Even though there are fewer sunshine hours in winter, because of the factors above, a solar power system will generate more than enough energy to meet the household or company’s needs.

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What is PV?

PV is short for photovoltaics (photo=light, voltaics=electricity). PV is a semiconductor-based technology used to convert light energy into direct current (DC) electricity, using no moving parts, consuming no conventional fuels, and creating no pollution.

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What is a photovoltaic (PV) cell?

A photovoltaic cell, or “solar cell,” is the smallest semiconductor element that converts sunlight into electricity. Each cell is made of silicon or another semi-conductor material, like a computer chip. The silicon is treated so that it generates a flow of electricity when light shines on it.

A stack of thin layers of semiconductor materials exhibit the photoelectric effect, such as silicon or cadmium telluride. The layers contain small amounts of doping agents (intentional impurities), such as the element germanium. The dopants give the semiconductor the ability to produce a current when exposed to light. Cells convert about five to fifteen percent of the solar energy they receive into electricity.

Solar cells are solid-state devices in which photons collide with atoms. This process transforms the resulting energy into electrons. These electrons flow into wires connected to the cell, thus providing electric current to appliances, lighting systems or other electrical loads. A typical PV cell is a thin 3″x3”, producing only a small amount of electricity.

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What is a solar module?

Solar modules, or solar panels, are a series of solar cells wired together into strings and enclosed in self-contained glass units for harsh weather protection. Solar cells are mounted into groups called modules that produce about 0.5 Volts of current to power lights and appliances. On the sunward side, cells are protected by a highly transparent solar glass pane. The underside takes the form of an insulating film or a second pane of glass. A connection socket picks up the generated direct current. Solar modules are connected together via cables, which link them to the inverter.

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What is a PV array?

A PV array is an interconnected system of PV solar panels that function as a single electricity-producing unit. The solar panels are assembled as a discrete structure, with common support or mounting. In smaller systems, an array can consist of a single solar panel. A complete set of components for converting sunlight into electricity includes solar panels, a support structure, wiring, a solar inverter, a solar regulator and other equipment.

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What is a blocking diode?

A blocking diode connects to the cable and prevents the solar panels from discharging the battery in the absence of sunlight. For example, a car battery will not act as an impedance load on a solar panel because of reverse blocking diodes that prevent nighttime battery discharging.

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What is PV conversion efficiency?

PV conversion efficiency is the ratio of the electric power produced by solar panels to the power of the sunlight shining on the solar panels. Cell efficiency defines how much energy in sunlight is actually converted into electricity. Amorphous silicon modules have lower efficiency than crystalline modules. Cell efficiency degrades progressively with use.

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When do I need a charge controller and why?

The safest way to figure out if you need a charge controller is to take Battery Amp Hour Capacity and divide this by the Solar Panel max. power amp rating. If the quotient is above 200, you don’t need a controller. If the number is less than 200 than you need a controller.

For example if you have a 100 amp hour battery and a 10 watt solar panel, you take 100 and divide it by .6 (600mA) and you get 166.6. Since this is less than 200 you need a charge controller. If you have a 5 watt solar panel in the above example you take 100 divided by .3 (300mA) and you come up with 333.3. Since this is larger than 200 you do not need a charge controller. However you still need a blocking diode, to prevent the battery from discharging to the solar panel at night. So as a general rule of thumb you don’t need a charge controller unless you have more than five watts of solar for every 100-amp hours of battery capacity.

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What kind of loads can I run on PV?

With a correctly designed PV system you can power almost any electrical load. However, as the load size increases the expense also increases. Loads like hot water heaters, air conditioners, room heaters and electric stoves should be avoided. The added cost of trying to power loads like these is very cost prohibitive. If these loads have to be powered it will be a lot less expensive to use energy saving appliances or use an alternative fuel type like propane.

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How much maintenance does a PV system require?

Very little. The solar panels may need a cleaning only if birds are a problem. If you have a flooded cell battery you should check your water levels once a month. If you have a sealed battery it will never need maintenance.

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Can I start small and add on later?

Yes. Solar is quite unlike a computer. If you start with a couple of good base components it is easy to add to your system later. First is to start with a good charge controller. Lets say you want to start with one solar module now. Don’t buy a charge controller that can handle one solar module. Buy a 20 or a 30 amp charge controller that can handle several modules. This will keep you from throwing away a small controller because you outgrew it. Most larger charge controllers cost less then two smaller charge controllers, so you will also save money.

The same principal goes for inverters. An inverter is a one time purchase. So think about what your needs will be in the future and buy something you can grow into. For example if you are looking at a 2500 watt 12 volt inverter. And you are using 80% of its power rating now you are not leaving yourself any room to grow. You may want to think about a 4000 watt 24 volt or 48 volt inverter. The higher voltages will save you in wiring cost but also mean you will have to add solar panels in 4 modules increments to make 48 volt.

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What makes up a PV system?

For a complete system you will need more then just a solar panel. Here is a short list of other components that might be required for your system.

Solar Panel Mount
Inter Module Wiring
Output Cable
Charge Controller
Fusing
Battery
Low Voltage Disconnect, This is built into most charge controllers
Inverter, For AC power

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What Kind of Inverter do I need?

The type and size of inverter necessary depends on your application. To determine this you must first calculate the maximum amount of load you will be running on the inverter at one time.

There are basically four size ranges of inverters. The first is 50-300 watts; these are small portable inverters. These inverters are ideal for laptops, small lights and other minimal draw AC loads.

The next size range is 300-800 watts. These are also somewhat portable and still have the outlets on the front of the inverter. This size inverter is good for small microwaves and other small appliances.

The third range is from 800-2000 watts. These units usually have battery chargers built into them. You can recharge your batteries with utility power or generator power. They are also great for powering medium size AC loads, or running multiple smaller loads at one time. These units are typically permanently installed.

The final inverter grouping is a permanently installed units ranging 2,000-11,000 watts. They function much like small generators, yet are completely silent in operation. They are great for your larger loads, such as refrigerators.

The other question that needs to be answered when selecting an inverter is the type of wave form. If you are running sensitive electronic equipment, like fax machines, laser printers or high tech stereo equipment you need a sine wave inverter. A sine wave inverter has a wave form that is very similar to the form of grid electricity. Other options may include modified sine wave, which is fine for items that are not supersensitive to clean power. You may experience a humming sound when powering clocks, and small radios on a modified sine wave inverter

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What Kind of Battery do I need?

The most common type of battery used in a solar system is a lead-acid battery. They are generally used because they have a low initial cost and are readily available. These batteries must be deep-cycle batteries. If the battery is a shallow cycle or automotive type it will not function correctly in the system. The deep cycle batteries are designed to discharge and recharge or cycle day after day for years.

The next decision is whether the batteries are sealed or flooded. A sealed battery never needs water added nor does it need an equalization charge. The benefits of this battery are; the battery can be mounted in any position and are easy to transport. The one downside is that they need to be monitored closely as to not overcharge. A flooded battery also needs close attention. The water level needs to be checked often and filled. You will also need to perform an equalization charge, which is a long steady controlled overcharge. This removes sulfation from the battery plates. While this restores the battery’s capacity, it can lessen the life of the batteries by warping the plates.

So you need to decide which battery fits your specific needs. As long as the battery is taken care of you can expect a long battery life using either battery type.

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Where should I mount the solar panels and what direction should I face them?

If your site is here in South Africa in the Southern Hemisphere you need to aim your solar modules to the true north direction (the reverse is true for locations in the Northern Hemisphere) to maximize your daily energy output.

For many locations there is quite a difference between magnetic north and true north, so please consult the declination map before you setup your mount structure. The solar panels should be tilted up from horizontal to get a better angle at the sun and help keep the solar panels clean by shedding rain or hail.

For best year round power output with the least amount of maintenance, you should set the solar array facing true north at a tilt angle equal to your latitude with respect to the horizontal position. If you plan to adjust your solar array tilt angle seasonally, a good rule of thumb to go by is latitude minus 15° in the summer, latitude in the spring/fall and latitude plus 15° in the winter.

What’s my incentive to invest in a solar power system?

Most people associate solar power with remote installations and off-grid implementations. In those cases the choice may be an easy one, but in towns and cities there are still reasons to turn to solar power as a supplement and an alternative to eskom or electrical utility grids.

With the unreliability of power in Africa it is a perfect way to become independent of the power grid. Another good reason is the reduction in utility bills. Once your system is working, it requires no monthly fees and little or no maintenance (and most parts are warranted). While it runs, it also reduces your electrical bills. Eventually it will pay for itself and keep saving you money.

Not only is your investment going to save you money and pay for itself, but solar installations frequently raise property value in both industrial and residential settings. Adding a solar power system to your home or business will also supplement the investment you’ve made in your property.

Another great incentive is city power and eskom starting to introduce rebates and incentives for implementing solar power systems.

Finally, solar power is a clean source of renewable energy. It reduces dependence on fossil fuels in a practical and effective way, and helps keep our environment clean.

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But where do I begin?

Getting started might seem like a daunting task, but it’s not as complicated as it first seems. With only an electrical bill, you can determine the minimum system size you’ll need. Once you’ve determined that, you can determine how many solar panels you’ll need, and find compatible components from there.

To begin, you’ll need the average monthly electrical use–which you should be able to find on your utility bill. This number will be in kWH (kilowatt-hours). Once you have that read through the solar design section you can calculate what components are needed.