The goal of this article is to explain how to install a small solar power generator. There are several options you can consider but, in this case, we will focus on a small solar power generator (<1 kWh / day), and simplify everything so that anyone can create a working system. However, be aware that trade-offs in terms of efficiency, safety and regulatory compliance can be made for reasons of simplification.
Steps
Step 1. Estimate how much power you need
To do this, decide which electronic devices you want to use and find out how much energy they use. Most devices have power ratings which can then be multiplied by the number of hours of use to get "watt hours" (Wh), units of power consumption. For example, if you intend to use a 15W device for 2 hours a day, the power consumption will be 15W x 2h = 30Wh. Note, however, that estimates are generally higher than actual energy consumption. To determine the actual quantity, an electronic counter can be used. Once you have all the watt hours, add them up. If the total exceeds 1000Wh (or 1 kilowatt hour), this article may not be for you.
Step 2. Determine how much unobstructed sunlight the location where you intend to install the solar panels gets
Unhindered means there are literally no shadows. If a nearby tree, building, or anything else casts a shadow in that particular spot, don't count the time the shadow persists. So if you have 12 hours of sunlight, but the sun is beyond the fence for 2 hours in the morning, then behind a tree for an hour at noon, then there is the shadow of your neighbor's house for 2 hours. hours before sunset, you will only have 7 hours of full light. Also, the days are shorter in winter. If you plan to use the generator in the winter, calculate the winter hours.
Step 3. Divide the total power consumption obtained in step 1 by the number of hours you calculated in step 2
If you decide you need 600Wh and get 6 hours of sunlight, the result will be 600Wh / 6h = 100W. This is the required amount of power you need to generate, per hour of sunlight, to meet your needs. To be sure, multiply this number by 2 or more. This is to account for the fact that solar panels only generate their rated power when they are pointed directly at the sun, and if they are fixed this will not happen most of the time. Due to other losses, you risk losing another 20% or more of the generated power. If you are expecting regular and prolonged cloud cover, it may be necessary to multiply by 5 or more (or simply reduce consumption).
Step 4. Buy solar panels
In general, there are 3 types of solar panels (strictly speaking, photovoltaic cells): amorphous silicon, polycrystalline and monocrystalline. Amorphous silicon panels are relatively inexpensive, little affected by small shadows, but they are very inefficient in terms of space (for the same power, amorphous silicon panels will be larger and heavier). Polycrystalline panels are more efficient, cheaper than monocrystalline, but also less efficient than the latter. Monocrystalline panels are the most efficient, but also the most expensive. The yield from mono and polycrystalline panels can be halved by even a small shadow, due to the way the individual cells are wired. Mono and polycrystalline panels can be purchased for less than 1 euro per watt.
Step 5. Consider "B-grade" panels, which are much cheaper but give good guarantees
Some would prefer their panels to last 25 years, but in reality the cost of photovoltaic cells is dropping so rapidly that replacing or converting the panels every 5-10 years is cheaper than paying more at first to get the ones that last. longer. If solar panels are too expensive for you, consider lowering your energy consumption. Giving up on some devices won't kill you (and if it does, this article may not be for you). Calculate the battery power you will need. To do this, take the estimated power consumption in step 1 and double it, because only half the power of the batteries should be considered usable to avoid damage. Then, multiply by the desired number of days to reserve. For example, if you want to use 600Wh, you need 1200Wh (or 1.2kWh) of power, so if you have 3.6kWh, you'll have reserves for a couple of days, even if the sun goes out (at that point, though, you might have other problems). Since most batteries have power expressed in Ampere-hours (Ah), it may be better to convert Wh to Ah. To do this, divide the power you calculated by the battery voltage: 3600Wh / 12V = 300Ah (divided by 6 for 6V batteries).
Step 6. Buy the batteries
Normal car batteries also work (at least for a while), but it is better to use "continuous cycle" batteries, generally sold for use in campers and boats. Some prefer the 6V batteries used for golf carts, which are designed to withstand repeated and deep discharges. If you use 6V batteries, connect two in series (positive pole of one connected to the negative pole of the other), then connect them in pairs in parallel (positive pole of one pair with positive pole of the other pair, negative pole with negative pole). If the budget allows, you can consider AGM batteries, which withstand wear better but also cost 2-3 times more than lead-acid batteries. Make sure the Ah values of all batteries connected together is higher than the power you calculated in the previous step. If using multiple batteries, make sure you have multiples of the same battery, and that they are all new (or remanufactured). Mixing different powers, models or batteries of different ages can reduce the life of all components.
Step 7. Purchase a charge controller
Charge controllers can cost anywhere from € 20 to more than € 100. The most important thing is to still use a charge controller. If you connect the solar panels directly to some batteries, they will recharge for a while, but they could also get damaged quickly. Whatever the charge controller is, it needs to support the amount of current produced by the solar panels. Most charge controllers are rated according to Amps, so divide the wattage of the solar panels by 12V (e.g. 200W / 12V = ~ 17A). Find a charge controller with a higher value than the theoretical estimate. This will give you a margin of safety and room for the future. In addition to this, the choice of the regulator will depend on an analysis that considers the cost, efficiency and life of the battery. More expensive charge controllers use different charging algorithms depending on the type of battery. They can also compensate for the temperature to better protect the batteries.
Step 8. If you plan to use AC power (that is, use normal wall sockets), you will also need an inverter
There are basically two types of inverters: modified sine wave and pure sine wave. Pure sine wave inverters give you a current closer to the city, but are generally more expensive (€ 90 or more for a 600W inverter). Modified sine wave inverters can be much cheaper ($ 40 or more for a 400W inverter), but some devices may not work, or work poorly with them. Also note that the inverters have an efficiency of 80-90%, which means that some power is lost in the conversion between DC and AC power. However, if you have followed all of the above steps as recommended, the system you have installed should have excess power to absorb this inefficiency.
Advice
- To get the most out of your solar cells, you can consider mounting them on a solar tracker.
- The secret to small solar installations is to reduce consumption.
Warnings
- If you're not more than careful, you could risk breaking (sometimes even expensive) devices. After all, you learn from these things, and you certainly won't make the same mistake twice.
- With small solar systems, it's easy to use too much power and cause temporary power outages. If you need large amounts of electricity, you should consider a more expensive and complex setup with more power and reserve.
- Electricity can kill, although touching both poles of a 12V battery usually won't be much worse than a static discharge, so don't freak out too much (electrostatic discharge can have voltages much much higher than 12V).
- Lead-acid batteries contain lead and acid. They can also emit hydrogen, which is explosive.
- Electric current can generate heat and excess heat can cause fires.
