WHAT YOU SHOULD KNOW BEFORE YOU ORDER A SOLAR POWER SYSTEM FOR YOUR FAMILY HOME OR OFFICE
FOURTEEN QUESTIONS, ANSWERS AND A STEP-BY-STEP GUIDE USING A SAMPLE INSTALLATION
This text was written in reaction to frequent customer requests for evaluations of offers they received for the delivery of a home photovoltaic power plant. They were asking what solar modules or battery storage to buy, whether one product is better than another and so forth. In the end, it always turned out that the offer, which came from an energy provider or distributor is only advantageous for that provider or distributor and not for the customer who is the actual energy consumer
1. How much electricity will my solar cells produce?
We can roughly say that 1kWp installed produces about 1MWh (megawatt per hour) of electrical energy in the Czech Republic per year. Using today‘s prices of electricity (Czech Republic, the year 2020), this means about 57 to 75 Euros. You don‘t like the strange kilowattpeak unit?
2. Production equals savings?
This is unfortunately not true for the following reasons, mainly. I can‘t usually accumulate all the energy produced for later. I will make more electricity during the summer sunlight hours than I am able to use or even store in the battery. I have to send the excess energy into the grid or leave it on the roof in the form of heat. The distributor won‘t pay me anything or very little for the energy I give him.
3. The efficiency of the solar modules – is it important?
In an industrial power plant that produces many megawatts it certainly does. In a household, where we’re talking about units or a few dozen modules, it makes no sense to chase microscopic differences in percentages. Whether a solar module or a solar tile has an efficiency of 18, 19 or 20% on paper is about as important as whether the normative consumption of a car in the manufacturer’s catalogue is 5.5, 5.6 or 5.7 liters/100km.
4. Does the country of origin matter? Are Chinese modules and solar tiles of a poor quality?
Based on our experience, it doesn’t matter whether modules/ tiles are Chinese, Korean, Japanese or European. You can take into consideration the country of origin for ideological reasons if you wish to support one company over another. Or if all other parameters are comparable and you don’t know how to make your decision.
5. What does “SHINGLED, PERC or HALF-CUT‘‘ mean? How about monocrystalline or polycrystalline?
PERC (Passivated Emitter and Rear Cell) technology means that a special layer is added to the back of the photovoltaic cell during production, which reflects the light back into the photovoltaic cell increasing its efficiency when lit from sharp angles, decreasing heat. In addition, this layer lowers the capacity of modules, meaning the overall resistance of the module.
6. What is the key when selecting a solar module then?
The answer is easier than you’d expect – if you’re buying from a renowned company with a history, tradition and good references, make your choice based on current availability, price per Wp, dimensions and the required appearance. Even a few millimeters in the width of a solar module is decisive in how many of them you can fit on a roof.
7. How to install modulesand solar tiles on a roof?
Your provider will use a special assembly system. There is no point today in trying to improvise with square tubes and a welding machine. You can get aluminum composite profiles for assembly easily at a low cost from a local manufacturer or distributor. They often have online configurators, which will calculate the quantity and type of material needed based on roof type, module size and their configuration?
8. Why is it not possible to connect electrical appliances directly into a solar module?
Parts, which are able to adjust the power from the solar modules to power in batteries and sockets are called regulators and inverters. Some manufacturers integrate the inverter, regulator and battery into one user device.
9. Batteries and how to best store electrical energy from the solar modules?
Let us leave aside the differences between individual types of batteries for now, as this issue was covered in detail in the article on batteries available on the www.gwl.eu website in Czech and English (https://shop.gwl.eu/battery-guide/). Let us focus on what the battery should be able to do if we are using it in a home solar power system.
10. What size of a battery to choose?
It depends on whether we plan to use the battery during off-grid mode (the house is not connected to the 230V mains) and the battery will therefore be the only source of power or whether the battery will only be a helper and we can rely on the energy supplier.
11. Other ways of storing electricity
Apart from a battery on the basis of chemical conversion (lithium, gel, VRLA,lead…), batteries based on a much simpler principle can be used for storing energy. Hot water is one that is used most frequently. Solar modules can be connected directly to some water heaters and this lets you get by without any electronics. The disadvantage is low efficiency of such a solution – it only works during direct sunlight.
12. How to keep the electrical energy in balance?
The flows of energy within the house or building should be governed so that we avoid blatant inefficiency. A battery will certainly help with this but it doesn’t solve all our problems – it’s expensive, has a limited capacity and is only able to charge from one phase. If you’re only starting to design your new home or a renovation, we strongly recommend connecting the solar power system project with.
13. Calculating ROI in the sample installation
Our sample installation annually produces about 6MWh of electricity of which it itself uses about 5MWh. This is therefore the energy, which the house doesn’t need to buy from the grid. Since it is in the Czech Republic, where the energy mix in the production of electricity contains about half of electricity produced from coal, the owners save on coal needed to produce 2.5MWh of electrical energy.
14. Conclusion and Summary energy in balance?
Combining appliances correctly into different phases, using a modern highly efficient LiFePO4 battery, a PLC module (e.g. Victron’s Cerbo, Solar Control’s WattRouter), accumulation into hot water and controlled switching on and off of other appliances (cooling of the cellar, pool filter) can achieve a state where almost all the energy that the solar power system produces will always be used in the house or building and no overflows occur.
Looking to buy new battery or solar equipment for your home, office or facility electricity backup? Let us know your questions.