Solar panels are not just for producing hot water. They are also used for producing electricity. With rapidly rising fuel costs the prospect of producing energy which is clean green and carbon free is becoming increasingly attractive.
In Spain solar panels produce a lot of energy even in the winter when we get clear bright sunny days. Photovoltaic (PVs) do not necessarily need bright sunlight to work. Even on a dull day a solar array will still be providing cheap green electricity.
The amount of power a solar cell produces is proportionate to the amount of light that it receives. Ideally we want to face our cells due south to receive the most light throughout the year. Any angle within 45 degrees of south will produce satisfactory results. Cells which are placed on a pitch between 20 and 50 degrees will yield best results.
Collectors can be framed panels which are the most common or solar slates which combine the waterproofing function of an ordinary roof tile with the PV function.
System Sizing
Before you attempt to size the PV array that you need first carry out a careful assessment of the present or expected energy consumption of the building and its occupants. Then look for ways to reduce this to a minimum. The less energy you need to generate the better.
The amount of electricity produced by a given panel is directly proportional to its surface area and the amount of direct sunlight that shines on it. So avoid shading from trees or other buildings.
When installing any device onto a roof whether it’s a new roof or retro fit check the loading carefully to ensure the structure of the roof is adequate to support any system. Always obtain the correct weights for the system you are using.
Inverters
Solar panels produce direct current (DC)electricity and most household appliances use alternating current (AC) electricity such as is provided by the grid. Unless you reequip yourself with DC appliances you will need an inverter to convert the DC to AC electricity.
A Giant Battery
If the system is connected to the grid a new metering system will need to be installed which can take account of electricity going back into the grid. Think, if you like, that when your electricity is fed back into the grid your meter needle spins backwards.
This is very convenient as it allows us to use the national grid as a giant battery. Energy can be “sold” to the grid at times when the building produces a surplus which is not being used by the occupants. When the solar arrays do not produce enough power for the building’s requirements power can be “bought back” from the grid.
It’s possible to achieve the aim of being net carbon zero over the cycle of a year without going off grid.
Off grid systems require storing electricity in lead acid batteries and I’ll cover that in another blog post.
Author: John Wolfendale
Bio: John is a founder of Eco Vida and is passionate about bringing modern design and construction practices to Spain. He believes a home which is warm in winter and cool in summer is largely a matter of design and selective use of materials. He is British and a Chartered Surveyor with 18 years’ experience living and working in Spain.
