They may produce clean energy once installed, but the process used to manufacture solar panels also burns fossil fuels, contributing to atmospheric greenhouse gases. So how can you be sure that solar panels do indeed offer a sustainable solar panels perth?
Luckily, working out whether solar photovoltaic cell (PVC) panels deliver clean energy can be determined relatively easily by calculating the Energy Yield Ratio (EYR) of each panel. That is the ratio of energy delivered over the lifetime of a panel to the energy required to manufacture it.
An EYR of more than one implies your solar panel produces enough energy to justify the environmental impact of its manufacture. It may therefore be considered an environmentally sustainable energy source.
Calculating the Energy Yield Ratio (EYR) of solar PVC panels
To work out the EYR of a solar panel you will need to know five things:
1. The amount of energy that was required to produce the panel.
2. The average sunlight intensity at the installation location.
3. The average daylight hours at the installation location.
4. The conversion efficiency of the panel i.e. how much sunlight will be converted into electricity.
5. The life expectancy of the panel.
Gathering input data from unbiased industry experts
PV FAQs, a document summarising research carried out in 2004 by The National Renewable Energy Laboratory at the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy, states that a typical silicon solar PVC panels requires around 420 kilowatt hours of energy per square metre (kWh/m2) to produce.
When estimating the amount of energy a solar panel produces in its lifetime, it is important to take into consideration the local conditions. Less sunlight means less energy produced.
Sadly, in the UK a lack of sunlight intensity is a general issue that must be accounted for. According to David JC MacKay, professor of natural philosophy in the department of Physics at the University of Cambridge, chief scientific adviser to the UK Department of Energy and Climate Change (DECC), and author of the freely available online book; Sustainable Energy — without the hot air (2009), the average light energy intensity in the UK on a south-facing roof is around 110 Watts per square metre (W/m2).
MacKay also conservatively estimates the conversion efficiency of typical solar PVC panels used in the UK to be between 10 and 20%. Of course, at Ardenham Energy our panels deliver towards the top end of that scale but, for the purposes of this exercise alone, let’s assume the worst and input a 10% conversion rate.
So, what is the real environmental payback for solar panels?
110W/m2 of light energy at a conversion efficiency of 10% means a solar panel has an energy rating of 11W/m2. In other words, in one hour, one panel will produce 11Wh/m2. Assuming a yearly average of 12 hours daylight per day, this would mean one panel can produce 132Wh/m2 per day, or just over 48kWh/m2 per year. Over the 25 years life expectancy of a single panel, this would add up to a total of more than 1200kWh/m2, nearly three times the 420kWh/m2 of energy required to manufacture the technology used to produce it!
In fact, we have taken the high road and been particularly unkind to manufacturers here. Even MacKay calculates an even more favourable EYR for UK installed solar PVC panels of around 4, and predicts that the trend towards more efficient solar technologies will produce ever greater conversion efficiencies in future.
The conclusion must therefore leave us in no doubt. Solar PVC panels deliver clean energy. Solar technology is proven effective as a sustainable energy solution.