Solar panels: with or without batteries?
Ask the Architect By Juan Pacheco
Surely, there shouldn’t be any disagreement that solar photovoltaic panels are the best possible source of energy, especially if you live in southeast Spain.
The installation of a photovoltaic system of solar panels in a domestic environment can provide numerous satisfactions, thanks to the lower dependence on conventional energy sources, which have a high cost, again, especially in Spain.
However, before opting for a specific type of installation we must make several decisions, such as the type of solar panels, the footprint area that the panels will occupy and, very importantly, if we are going to have batteries to store the surplus energy production or not.
At first glance, the latter seems convenient, since, with sufficient infrastructure, it would allow us to stop relying entirely on an external commercial supply. However, batteries do not last forever, and their cost is high, so that their amortisation is a factor to consider if we want our solar panel installation to be truly profitable.
Batteries or no batteries that is the question
Batteries or accumulators, as in a car, store the electricity generated during daylight hours, so that it can be supplied at other times, such as at night or during cloudy days, where production may be less than necessary. This gives us the long-awaited autonomy of people who seek not to depend on external electricity companies, which means paying for consumption and numerous expenses and taxes.
The batteries for solar panels resemble those of cars, and have a charge regulator, which allows electricity to enter when they are not full, and prevents its entry when they are full, thus prolonging their useful life by avoiding overloads.
There are several types of batteries, some more interesting than others depending on their use and the dimensions of our solar panel system. Logically, the number of batteries will depend on how much energy you need to store over a day.
Small or medium-sized installations usually use monoblock batteries, including gel and AGM (lead) batteries. Their useful life is around 10 years, at the end of which they must be replaced with new ones, although their price is not as high as other more sophisticated batteries. On the other hand, lithium batteries are somewhat more expensive but last longer.
In the case of a larger installation, longer-lasting batteries, such as stationary ones, are preferable. There are several types available that can offer double the life of mono-blocks. Their price is also much higher, and they use advanced technology, such as the Tesla Powerwall. The use of one or the other will require the advice of a professional.
Are they profitable?
The important previous question is whether or not it is going to be profitable to use batteries. If you do not have them installed, you will need to maintain a connection with the conventional electricity network, and will only pay for the electricity you consume, i.e. that which your solar panel system has not been able to provide. When the latter produces more electricity than you consume, the surplus will be injected into the network and you must be compensated for it, either economically or with a reduction in the amount of subsequent invoices, depending on the current legislature.
Specialists believe that, at present, batteries are still too expensive and that in many cases it will be more convenient to remain connected to the conventional network. But this could change in the future. As more and more photovoltaic systems are installed, their prices will fall. If the batteries reduce in cost by 50 percent, then it could be profitable to use them, even taking into account the necessary renewal at the end of their useful life, because the savings will be higher.
For homes and applications that are far from the power grid, however, the solar panel system plus batteries will be the only possible option however, it is strongly recommended that you obtain a previous study from the installation company so that you know what the return period will be and thus select the most appropriate type of batteries.
British and Spanish qualified Architect
Juan Pacheco Moreno Bsc (Hon), DIpArch. (R.I.B.A.) arquitectojapm@gmail.com
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