How Solar Energy Works

Our planet revolves around the sun at just about the perfect distance to provide the optimum conditions that sustain life. The light from the sun contains vast amounts of energy, which, when it hits an object, causes heat to be transferred.

But with some materials found on Earth, sunlight has another, equally profound effect – it turns on the lights.

How a solar cell works

How a solar cell works

Take silicon for example. As the sun strikes it, electrons are dislodged and, when these little things start moving, you get an electric current. The amount of electricity produced depends to a large extent on the purity of the crystal used. With top of the range silicon photovoltaic cells, the efficiency is around 20-22%, which means they convert that percentage of light to electricity. For the production of our solar panels that can affect the cost as well as the efficiency.

Solar power is a renewable source of power, meaning it has an unlimited source and we can use it to provide sustainable, and clean, electricity rather than depend on fossil fuels such as coal and oil. The challenge is to find a way of harnessing this power intelligently and making it more efficient and cheaper to access. At the moment, we use large solar panels that incorporate silicon photovoltaic cells, but in the future we may be able to produce cheaper and more carbon friendly materials that do the job better.

How Solar Energy Powers Our Homes

Unless you have been living in a cave for the last twenty years, you’ll know that we need to find greener ways to live. You’ll also have noticed those glass panels on top of roofs where people have solar panels installed. These are usually south facing to collect the most sunlight and their purpose is to generate electricity. The photovoltaic cells inside a panel create a DC current which is then fed into an inverter that changes it to AC. That can then either be used to power a house, stored in batteries, or passed onto the National Grid to provide energy for other uses.

Several things influence how much electricity an array of solar panels produces. First, it needs to be at the optimum angle and facing the right way. Secondly, the quality of the photovoltaic cells make a difference and often influence the size of the installation. Most homes use a lower grade silicon that has about a 13% efficiency, mainly because it is cheaper but still provides the level of power needed. Finally, the more panels you have and the bigger the array, then the more electricity you will have the potential of producing.

You can expect a domestic solar panel installation to last between 20 and 25 years and they have started to become more popular in recent years because of government initiatives such as the Feed in Tariff which means you can earn money back by selling the power you generate to the energy companies. A typical solar panel installation would cost around £7,000 and earn you around £6-700 a year with savings on electricity bills and profits from the tariff.

Solar Energy on a Grand Scale

It’s not just on roofs that you see solar panels doing their stuff. Over the last few years solar farms have started to proliferate. Acres of land have been taken up by huge arrays of panels that provide valuable electricity for the grid. Despite recent cuts in government subsidies, green technologies in the renewable industry are still thriving and for many landowners having a sizeable solar farm installed offers a chance to help the environment and make a profit at the same time.

Solar Farm

Solar Farm

One of the largest solar projects in the UK is at Wymsewold Airfield in Leicestershire that has 130,000 panels producing 35 MWp, but by far the biggest, so far, is located in the Mojave Dessert in the US and boasts 350,000 panels that provide electricity for around 140,000 homes.

Solar farms are also being funded in a variety of ways. In some places, communities are coming together to find the money themselves, whilst with other developments companies are willing to take on the investment and installation in exchange for the Feed in Tariff, paying the landowner a rent for use of the land. As with most large scale, renewable technologies, solar farms have their detractors, mainly from people who think they are an eyesore or are believe they are not as efficient as many make out.

How Much Energy Does Solar Provide?

An average solar array on top of your roof should provide around 3,400 kWh per year, depending on the size and the type of photovoltaic cells used. According to statistics though, the total solar energy production in the UK last year only amounted to around 0.64%, compared to 8.7% for wind power. The reason may well be that more has been invested in wind farm development, both onshore and off.

A more startling statistic is that solar energy seems to have increased rapidly over the last two years, providing just 77 MW in 2010 but exploding to 3,375 MW in 2013, perhaps due to government initiatives to reduce our carbon footprint.

As a localised source of energy, solar panels have a few more advantages than some of its renewable counterparts such as wind. First of all, and maybe most importantly, it can be fitted onto the roof of a house. The right system can provide all the electricity needs for a home and may even produce an excess that can be fed into the National Grid. Because homeowners and businesses can earn a profit and get a decent return on investment with their installation, it is often seen as a good option for those wanting to simply reduce their fuel bills and / or make a little money on the side.

Solar Energy Myths

It takes more energy to create a solar cell than it actually produces in your solar panel array.

The misconception is that solar cells are, secretly, not a green technology. Yes, we need to use energy to create them in the first place and there are some processes that need to be improved, but your average solar cell will probably return that initial investment in the first 2 to 3 years of its life.

Solar panels need a hot, sunny day to work properly.

Actually, that’s not strictly true. Solar panels work at their optimum at lower temperatures than you get in the dessert and the UK is just fine for producing electricity from them and they even produce on cloudy days.

Solar power means an unstable electricity supply.

Far from it. If you have the right size array for your property you will probably make excess for your needs. Even so, you will still be connected to the grid and any shortfall can be made up from there. Other myths are that solar power can’t run a big building. Again, the right array can power a whole factory.

Solar energy is too expensive.

Yes the initial cost of installing solar panels may seem daunting to some but the return is pretty good with the Feed in Tariff and savings on energy bills – you could be making extra money and have paid off your loan within 6 or 7 years. And there are different ways you can fund your solar panels installation including the Green Deal and even having them put in for free.

The weight of the panels damages your roof.

Your installer will assess your roofs capacity to hold the weight of the panels, a frame is built that anchors onto a number of rafters so the weight is spread out and won’t damage the roofs supporting structure underneath. Also solar panels are reducing in weight as time goes on and manufacturing processes improve.

Solar panels need a lot of maintenance.

Again this is not strictly true. If you’ve had your array installed by a reputable company then your panels should last for the next 20-25 years. Yes, they will need a regular maintenance plan but so does your boiler – solar panels are pretty robust and don’t have that many moving parts that can go wrong.

Installing solar panels is complicated.

In fact it isn’t. A reputable installer will normally undertake a free consultation and take you through any issues and paperwork. The actual installation can be done in less than a week (normally 1 or 2 days). Tying into the Feed in Tariff and earning an income is also simple and, once you are registered, you can start benefiting from that extra income.

Solar panels will reduce the value of my house.

There is no evidence of this. Actually, with people’s awareness growing and an increasing desire to incorporate renewables into our everyday lives, having solar panels may well increase the value of your property and recent studies show this to be the case.

It is hard to remortgage a home or get a mortgage with solar panels.

This is not true, many people have sold and bought properties with solar panels on the roof and they have little or no impact on a mortgage company’s decision to provide the finance. The only issues that may arise are if the array has not been MCS certified or has a complicated ‘Rent-a roof’ (free solar panels) scheme attached to it.

Picking the Right Installer for your Solar Panels

As you might expect, solar panel installation is a growing industry, fuelled by the increase in people who want access to clean, renewable energy that reduces their reliance on energy companies and fossil fuels. As with any industry, there are good and there are bad companies, so if you are looking for the right one there are some top tips that you should keep in mind.

First of all, a reputable installer will have the right certification and in the renewable energies world this is pretty specific. They should be part of the Microgeneration Certification Scheme and they should also be members of the Renewable Energy Consumer Code. Other bodies include the Renewable Energy Association and the Solar Trade Association.

Micro Certification Scheme Logo

Microgeneration Certification Scheme Logo

These certification bodies also stretch to the manufacturers of solar panels – if you want to avoid substandard or poor performing arrays then make sure they carry the certificate marks.

As with any big project, you should be looking to get a number of quotes from different installers and they should do a full survey of your site to make sure it is suitable for a solar panels array. Things you will need to consider:

  • The load bearing capacity of the roof – as mentioned previously, most modern roofs should be able to take a solar panel installation but you should make sure and get independent advice if you are not totally confident. The general rule is that if installing a panel array increases the load by more than 15% you will need formal building approval, usually from the local council.
  • Do you need a south facing roof? Technically, yes you do. Though this may be about to change. South facing provides the most access to direct sun. But in Germany, builds are starting to include east and west facing panels which provide more coverage throughout the day for the grid. It might be that in the near future, there will be government subsidies and incentives to build on east and west facing roofs.

The Future of Solar Energy

Developments are afoot in the world of solar panels. The race is on to find cheaper and more efficient alternatives to the heavy duty silicon photovoltaic cells. That includes window glass that can double as a solar panel and new materials such as plastic that can be used to replace the existing technology.

Another area where advances are being made is in the manufacture of panels which, in the past, has come under attack for being less than carbon friendly. One of the main components has been the toxic substance cadmium chloride but this could well soon be replaced by the salt magnesium chloride which is a lot safer and cleaner to use.

Whilst scientists are searching for cleaner and cheaper ways to produce photovoltaic cells, others are thinking big. Californian based company Solaren are looking at the possibility of giant panels beaming down our power from space in the future.

Meanwhile, the battle to harness the sun’s energy goes on. While more households start to seriously consider the benefits of having solar panels on their roof, and businesses seek ways to reduce their own carbon footprints, there’s no doubt that the industry itself is beginning to thrive.

Find out all you need to know about solar energy here.

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