Electricity Straight From The Sun – Photovoltaic Power

Protection from rising fuel costs, the prospect of being sent a cheque by your energy company, and the knowledge that they are using clean carbon free energy are factors making many people look into photovoltaic energy. This article sets out some of the basic facts.

Where to put them?
Whilst a solar cell will produce the most energy on a bright sunny day it will still produce clean cheap electricity even on dull days. The amount is proportional to the amount of sunlight and of course the surface area of the solar panels. Here are some of the factors you need to think about when locating and setting up your panels:
1. Orientation (south in the northern hemisphere)
2. Angle (any angle within 45 degrees of due south is ok)
3. Avoid shading from trees / hillsides
4. Check the loading if you’re thinking of putting them on the roof
There are two types of collectors: framed panels and solar roof tiles. Panels are by far the simplest to install. Solar tiles which are just clipped into the base tile after the completion of the roof might be a possibility on a new build but are considerably more expensive. Either type of collector could compromise the architecture.
Aesthetics may be a consideration too depending upon the size and positioning of your array and the locality. Big PV arrays are pleasing from a carbon efficiency point of view but in our experience are understandably unpopular with national park authorities who want to protect the natural scenery.
System Sizing
The first job is work out how much electricity you need. The second job is to work out how you can consume less. It’s far more cost effective to use less than to generate more. It also helps ensure there are no disappointments once the system is up and running.
Batteries and the Inverter

High Speed Inverter H320 Series 62
High Speed Inverter H320 Series 62

Solar panels produce low voltage DC electricity so you will need an inverter to convert the electricity into high voltage AC energy. The inverter is sized appropriately for the solar installation.
If the installation 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. Really you can think of the grid as a giant battery. Electricity is sold to the grid when you have a surplus and bought from the grid when the solar arrays do not produce enough for your needs.
Do you fancy the good life? Or perhaps you are in the middle of no-where. Off grid installations need a battery storage system to balance out the mismatch between when you want to use your electricity and when the sun shines. Lead acid batteries are the most pragmatic currently but a lot of money is being spent on research into a new generation of batteries and hydrogen fuel cells so the technology is changing.
Off Grid Wood Fire Hot Tub
Off Grid Wood Fire Hot Tub

You will need to decide how many days of electricity you want to store. A typical system would be designed for 3 days. It’s important to note that it’s very uncommon to rely 100% on photovoltaic electricity for modern living. Most off grid systems have some kind of hybrid system with wind or some other source as a back-up including, day I say it, diesel generators.
Carbon and Financial Payback
One concern many people have is that over the life cycle of a solar cell it will produce less energy than was used in producing it. This is not the case. The carbon payback period is controversial and highly dependent on location and exposure.
Similarly people ask about the financial payback of photovoltaic systems. Obviously it depends on the cost of installation and whether there are any factors which push up the cost. As a very rough guide you may be looking at 10 to 15 years as a financial payback and most solar cells have a guarantee from the manufacturer of 25 years and should go on much longer.
The key thing is this. Energy costs are not falling. In fact they’re going up. Oil is a non renewable source. It’s going to get more and more expensive to extract and will eventually run out. So even if carbon emissions are no threat to the environment installing a photovoltaic system could be a wise move.
Author: John Wolfendale