Much of the interest in photovoltaic systems tends to be naturally focused on the generation of electricity to provide light and power to a private household or public building. And indeed, at AbleSkills Renewable Energy Centre, solar PV courses, foremost amongst all the City & Guilds / BPEC / NICIEC renewable energy courses offered, have quickly established themselves as a popular choice with entry level candidates and experienced electricians who want to add solar panel installation to their service knowledge and skills.It's not surprising, of course, as the FeedInTariffs Scheme (FiTs) continues to be a major incentive, successfully driving domestic solar installation and consequently, demand for trained and qualified solar PV electrical fitters is on a dramatic rise as the UK industry grows month by month.However, with the launching of the Renewable Heat Incentive(RHI), the spotlight is on the other key important requirement - water heating. A recently published report indicates that there could be as much as a 700 per cent increase in renewable heat capacity in the south west of England, alone, over the next ten years! And this means - significant business and employment opportunities for those who have completed their training and qualified on solar courses.According to the research, there are some 4,000 renewable heat installations currently in the south west, but it's forecast that by 2020 there could be more than 140,000 projects, of which, 136,000 would be in domestic premises. Under the UK's renewable energy target of 15 per cent set by the EU, the DECC expects renewable heat to contribute around 11-12 per cent while electricity to produce 30 plus per cent by the end of the decade.It's important to know there is a difference between solar panels that convert sunlight to electric power and other types of solar panel, which have the capability to convert solar thermal energy to heat household water.All solar energy water heating systems perform the same basic functions of gathering heat in a solar collector, transferring the heat to the water supply and then storing the heated water until ready to be used. In addition to heating the water, solar space heating can use solar thermal energy to heat the space inside a building. Active solar space heating systems are predominantly liquid systems but air systems can also be used to capture and convert the sun's thermal energy.The solar collectors used are the same for both liquid space heating systems and domestic solar water heating. The most common type of solar collector used?