There are currently two different types of solar panels for domestic and commercial use, one is to heat water and the other is to produce electricity. The solar panels for water are used more in the United Kingdom as they seem to produce the most cost benefits to the user. Due to the climate in the United Kingdom and the lack of continuous sunlight, solar panels generally work best between the months of May to the end of September when the sun is at its highest in the sky. The average home will need around 5 sq meters of solar panel to supply enough heat for their everyday hot water use. To extend the time zone by one month either side to include April and October you will need to have up to 20 meters of solar panel which will produce far too much hot water in the hotter months and then this will have to be discharged as this amount of hot water would be impractical to store. So the sizing for solar panels is very important to get right. There are two types of hot water solar panels, one is a blackened box with pipes running through it like a maze, the water is pumped through this box, the sunlight streaming in heats the box and the pumped water warms up by the time it flows through the exit. The other type of hot water solar panel is made up of a system of evacuated tubes, these are tubes made from borescope glass (pirex) and they are made just like a thermos flask twin walled with the air removed so the sun’s radiation passes through it more efficiently. Inside the glass tube a sealed copper rod is fitted, this rod has a small amount of pure fluid inside and then the air is sucked out to create a vacuum, then the rod is sealed. The fluid inside the rod boils at a much lower temperature than normal fluids, because of the lower air pressure in the rod, when the water boils it travels to the tip of rod then condenses, returns, and then the cycle continues (providing there is still sunlight). These types of solar panels work really well on partly cloudy days because the tips of the rods continue to cycle whilst the clouds pass over. The tips to the tubes insert into a header where water passes through, so the hot tips of the rods heat the water passing through. The average house will need to have 20 to 30 evacuated tubes installed. The main advantage of this type of system is that if a tube breaks it can be replaced independently. Both these types of solar panels work best in conjunction with solar hot water cylinders, most homes have some form of hot water storage. These are mainly heated indirectly by utilising a separate gas boiler. The water heated by the boiler passes through a copper coil inside the cylinder and indirectly radiates the hot water from the pipe to the water in the cylinder. A solar cylinder is different as it will have two copper coils, one at the bottom of the cylinder for the solar coil and one at the top for the boiler.In this configuration the solar coil is always used as a pre-heat, heating the water at the bottom of the cylinder, even on cold days because the in coming mains water could only be around 8 degrees. Even on most days in the winter the average solar panel, will achieve higher temperatures than this, thus slightly heating your cylinder. Hot water cylinders need to get to a temperature of 60 degrees once a week for 30 minutes to kill off bacteria and legionnaires disease etc. This is where the boiler connected to the top coil in the cylinder can come into play. If there is, for example, a spell of bad weather, the boiler can be set to come on once a week to boost the cylinder for 30 minutes at 60 degrees. Modern day solar panel installations also include pressure vessels for the expansion of the heated water, programmable temperature difference controllers, low energy water pumps, expansion valves and some form of heat dump i.e. to a radiator. The photovoltaic type of solar panel is used to create electricity mainly 12 volts; these are manufactured using labour intensive methods. They are generally made up of micro thin wafers of silicone panels connected in a series. Then the solar panels are connected to a bank of batteries to use as a storage system. This is then converted to normal household voltage using an inverter to step up the power.These solar panels are well suited to more of a sunny climate because of their expense in manufacturing, and less likelyhood of needing to heat homes as frequently as it necessary in the UK. There is now a new form of solar panel being produced called thin film solar. It is manufactured the same way as a newspaper is printed; just by simply printing on a continuous backing. In the case of these new solar panels the backing is a thin aluminium sheet, the cigs (copper indium gallium selenide) is the conductor and is printed just like an ink on paper. This new form of solar panel is not as efficient as silicone based solar panels but the cost in manufacturing is significantly lower and incredibly faster to produce. These solar panels can be formed into many shapes and sizes unlike the silicone based panels and, no doubt. we will all be hearing more about this in the future.
