SOLOSOL - Electricity Basics
Before purchasing a ‘photovoltaic’ renewable energy system, it is a good idea to have a basic understanding of electricity. Simple familiarity with basic electrical terms and concepts will enable you to better understand your renewable energy system and use it with confidence.
The building blocks of an electrical vocabulary are voltage, amps, resistance, watts and watt-hours. Electricity can simply be thought of as the flow of electrons (amperage) through a copper wire under electrical pressure (voltage) and can be thought of in terms of the flow of water through a pipe. If we think of copper wire in an electrical circuit as the pipe, then voltage is equivalent to pressure (psi) and amps are equivalent to flow rate (Litres per minute).
To continue with our electricity to water analogy, a battery stores energy much as a water tower stores water. The taller the water tower the higher the pressure you get at the base. As the water is consumed so the pressure drops, most water towers are mushroom shaped, providing most of volume and pressure at the top. Although a 12 volt battery is not physically shaped like a water tower, it has most of its stored electricity available between 12 volts to 12.7 volts. When drained below 12 volts, little amperage remains and the battery voltage will decrease rapidly.
In a simple system, a power source like a solar module provides the voltage which pushes the amperage through a conductor (wire) and on through a load that offers resistance to the current flow which in turn consumes power (watts). Power is measured in watts and is the product of voltage multiplied by amperage. Energy is power (watts) used over a given time frame (hours) and is measured in watt-hours or kilowatt-hours (1 kilowatt-hour equals 1000 watt-hours). For example, a 100 watt light left on for 10 hours each night will consume 1000 watt-hours or 1 kilowatt-hour of energy. A kilowatt-hour is the unit of energy measurement that the utility company bills you for each month. Electrical appliances are rated in terms of how many watts (or amps) they draw when turned on. To determine how much energy a particular appliance uses each day, you need to multiply the wattage by the number of hours used each day.
Parallel and Series Wiring
When wiring solar modules or batteries together in a renewable energy system, remember that connecting two of them in series (+ to -) doubles their voltage output, but keeps their amperage (or amp-hour capacity) the same. Connecting two of them in parallel (+ to +, - to -) doubles their amperage output (or amp-hour capacity), but keeps their voltage output the same. For example, most solar modules have a 12V nominal output so you would need to wire two of them in series (+ to -) to charge a 24V battery bank. The amperage output from these two solar modules in series is the same as that of a single 24V solar module. Similarly, you would need to wire two 12V 950 amp-hour (AH) batteries in series (+ to -) to configure them for 24V operation to obtain a 950 amp-hour 24V capacity battery.
Wire Sizing
Equally as important as understanding voltage, amps, resistance, and watts, is the understanding of the importance of wire size. Having collected your solar energy, you do not want to loose it through undersize cables and the resulting voltage drop. The amount of current that you can send through any electrical circuit depends on three things; the size (mm2) of the wire being used, the voltage of the system and the one way wire run distance. The longer the distance and lower the voltage, the larger size wire you will need to use to minimise the voltage drop.
As a "rule of thumb", if your solar array consists of 4 or more, 60 watt or larger solar modules and is 20 metres or more away from the battery bank you should consider setting your system up at 24 or 48V instead of 12V.
Solosol specialises in installing off-grid photovoltaic systems in remote locations. We offer complete, cost-effective solutions, ideal for rural properties or log cabins where connection to the grid is not feasible. We save you money, without compromising on quality, by installing top brand products including Outback inverters, Kyocera solar panels and Exide deep cycle solar batteries.
Energy that doesn't cost the Earth...
Solar cells are long lasting sources of energy which can be used almost anywhere. Solar cells provide cost-effective solutions to energy problems in places where there is no mains electricity.
Compared to other renewable sources, they also possess many advantages:
Very reliable: Kyocera modules have a 25 year warranty and a considerably longer life expectancy. The theoretical lifespan of solar modules is 100 to 125 years. The first modules ever manufactured are still producing power after 50 years of service.
Environmentally Friendly: Over its lifetime a single gram of silicon can produce 3,300 kWh of electricity without releasing life threatening toxic and radioactive substances. A single gram of uranium can produce 3,800 kWh of electricity. However, a uranium atom can only be fissioned once, whereas a silicon solar cell can absorb photons repeatedly to generate electricity. Gram for gram, silicon and uranium produce comparable amounts of electricity.
Green Energy: Solar power is an environmentally friendly energy source. By not using fossil fuels to generate electricity, a 1Kw solar power system will prevent about 25 tons of carbon dioxide emissions over its life. That is equivalent to planting about an acre of trees.
Low cost: Calculated over the life expectancy of solar modules, solar power becomes one of the cheapest, hassle-free and pollution-free energy sources available.
Inflation proof: Your investment in solar energy protects you from the spiralling cost of energy. Since January 2004, average (UK) household energy bills have risen by 69% or £407. The average joint bill for gas and electricity now stands at just under £1,000 a year per household. Gas bills alone have risen by 85%. Electricity-only customers have seen 50% rises. In the past year each of the power companies have increased prices twice, with three rises from npower.
