New technologies mean that solar energy can be harnessed more effectively than ever before, maximising the potential that solar energy has to offer.

Solar thermal heating systems are one of the most cost effective and environmentally friendly renewable energy resources available.

A solar thermal hot water system heats water for domestic or commercial use by harnessing the infrared energy present in daylight. This abundant source of free energy quickly heats up fluid in a solar panel (also called a solar collector). A small pump circulates this fluid through a coil in the hot water cylinder and heats up the water. During the winter months there is not enough energy available to fully heat the water so the existing heat source (boiler or immersion heater) automatically tops up the stored water temperature.

Installing a solar water heating system is equivalent to taking a small car off the road each year in terms of pollution reduction. The system can contribute to savings on your fuel bills and help make the environment cleaner by reducing the use of fossil fuels and thereby help reduce CO2 (greenhouse gas) emissions.

Financial benefits to the consumer include:

  • Immediate and substantial savings on hot water bills.
  • Extended boiler life.
  • Save on fuel tax.
  • An excellent ROI (Return On Investment).
  • Adds value to property.
  • Attracts a cash back grant.
  • Pays for itself inside 15years on bill savings alone (set to reduce)

Water heating (domestic and commercial) is perhaps the most cost-effective overall application for solar energy in the UK. A properly sized thermal installation will provide 60% to 70% of your annual hot water needs. This generally equates to 100% of the demand in summer months and around 20% of demand in winter. This is because the daylight hours are shorter in winter with lower light levels.

There is a demand for hot water in the home all year round and it is theoretically possible to fit sufficient solar capacity to provide 100% demand in winter. This would result however in a very large surplus in summer, which would effectively be wasted and there it does not therefore make economic sense to install a system of this size.

In winter a supplementary heating system is required to ‘top up’ the hot water system. Obviously the most cost efficient system needs to be selected and this is usually the existing hot water system.

In effect a solar heating system will provide a significant reduction in your energy bill.  Such a system can provide central heating energy, domestic hot water or a combination of the two and is achieved by a device called a ‘Thermal Store’.

Harnessing renewable energy from the Sun

This graphic shows the total UK solar irradiation in Kilo Watt hours per square metre. Dependent on the geographical location of your property, every square metre of your house or garden receives between 800 and 1200 kW hours per year of solar energy, energy which is completely free. Interestingly the UK actually receives something like two-thirds of the solar irradiation experienced at the equator.

Whilst no one is able to claim that the UK can benefit from solar energy to the same extent as other parts of the world, as say in Africa, there are still considerable amounts of free energy that a modern solar energy system can extract with a high degree of efficiency.

New technologies mean that solar energy can be harnessed more effectively that ever before, maximising the potential that solar energy has to offer.

Key benefits include:

  • All solar systems work best with direct sunlight but also work effectively with diffuse light.
  • Solar systems are able to operate 365 days a year in the UK to different levels of efficiency.
  • Solar energy is free and is the most abundant energy source on the planet.
  • FirstLine Digital specialises in the integration of solar thermal panels with existing domestic systems to provide cost-effective solutions that provide tangible benefits and advantages.
  • Millions of households in the UK can realistically benefit from the installation of modern solar thermal technology. However the benefits, gained compared to the cost of installation varies considerably from property to property. FirstLine Digital can provide advice on the best and most economic system for your home.

How it Works

In its simplest form, a solar thermal system works by solar panels (known as collectors) absorbing as the sun’s heat. These panels in turn contain liquid, which once heated travels to a coil in the hot water cylinder and transfers heat to the water store. Over a period of time, a full tank of hot water is generated – the time period being dependant on the intensity of the sun, the size and efficiency of the solar panels and the size of the hot water tank.

As can be seen in the diagram above, the tank has a seperate heat exchange coil which can be used to provide supplementary heating when solar energy is not available or inadequate.

A typical system is made up of:

  • Solar collector (panel).
  • Hot water store (normally a twin coil tank).
  • Flow and return pipes (solar primary).
  • Heat exchange fluid.
  • A means of circulation and control.
  • A means of coping with temperature fluctuations from -15′c to 250′c.
  • Means of control of the legionella bacteria.
  • Delivery of the hot water to outlets.

In turn, there are two types of solar collectors (panels):

  • Flat plate collectors (in-roof or on-roof)
  • Evacuated tube collectors

Flat plate collectors are similar to a ‘Velux style’ roof window and consist of fluid filled metal ‘envelope’ with a selective black coating that greatly improves absorption of solar energy. This is housed in a glazed, insulated box. The collector is mounted usually on a roof and connected to the hot water system in a similar way to a conventional boiler, using insulated pipe work that feeds a coil in the hot water cylinder.

Water is circulated by either thermo-syphon or, more commonly using a circulating pump. The pump is controlled in such a way that when the temperature of the collector is lower than the temperature in the hot water system the pump is switched off. Flat plate collectors need to be protected against frost, something easily achieved by the addition of antifreeze to the heating circuit, or by arranging the system such that the collector drains down when the pump is switched off. A typical 4 person household would require 3-5m2 of panel.

In turn, evacuated tube collectors consist of around 20 vacuum tubes typically around 10cm in diameter and 2m in length, mounting onto the roof plane on a framework. Each vacuum tube is fitted with a heat transfer fluid, the upper ends of which are connected to a manifold heat exchanger that is connected to the primary circuit of the building.

Evacuated tube collectors are more efficient than flat plate collectors – typically 3m2 of flat plate is equal to 2m2 of evacuated tube. Although more expensive to purchase, evacuated tube can be less time consuming to install and are less ‘position sensitive’. They also have the added advantage of being suitable for fitting to outside walls.

Typical costs

Typical cost of supply and installations £3,000 to £4,500

Grants

Unfortunately as of 06.00 am Monday 24th May 2010, the Low Carbon Building Programme (LCBP) was closed to all new applications.

If you would like to find out more please contact us today on
+44 (0) 8714 333 333 to discuss your requirements and to find out more about our Solar Thermal technology services.

Related Links

Energy Saving Trust Housing Programme
Solar Trade Association
The Carbon Trust