Gemini Solar UK Ltd

 Solar PV, Solar Thermal

Microgeneration Certification Scheme

Tel: 01286 675718

Solar Thermal Systems

Solar Hot Water 

What is it?

Simply put solar hot water heating is the technology system used to enable the sun’s energy to heat your hot water. Water is circulated from the hot water cylinder to the solar panel usually fitted to your roof. This water heats up which in turn heats the cylinder and stores the energy produced. It can then be drawn off when required. A secondary heating method is still required to top up your water during the winter months. Log burning stove, conventional gas or oil boiler or immersion heater.

Gemini supply and install

We are very experienced in solar water heating our team have 30 years of installing solutions from single dwellings to commercial multi panel systems. Gemini are able to design systems of all sizes for all applications. 

We offer competitive and innovative nationwide installation service. We are able to survey properties with a home visit or via satellite technology. After business hours vists are no problem.

Solar thermal Collectors

Flat Plate Collectors.

Flat plates offer an efficient and reliable system and also have the advantage that they can be integrated into the roof therefore making the system look more aesthetically pleasing.  It is also possible for the flat plates to be manufactured to any shape or size, this will advantageous if the roof is awkward shape.

Evacuated Tube Collectors.

The vacuum tubes consist of a double wall glass tube (made from strong borosillcate glass i.e. Pyrex) with a space in the centre which contains the pipe with fluid in.

The sun's radiation is absorbed by the selective coating on the inner glass surface but prevented from re-radiating by the silvered innermost lining. This is in effect like a one way mirror which has been optimised for infra-red radiation. In fact it is very efficient, of the sun light’s energy hitting the tube’s surface 93% is absorbed with only 7% is lost through reflection and re-admission.

The presence of the vacuum wall prevents any losses by conduction or convection – just like a thermos flask. Because of this, the system will work even very low temperatures unlike a flat plate collector.

If the roof is not due south then with evacuated tubes it is possible to rotate the tubes individually to locate the optimum angle or orientation. The evacuated tubes will be more efficient than the flat plates during the spring and autumn periods. This is because there are minimal losses between the glass tubes and the absorber, thus enabling the collector to convert low levels of radiation into useful energy. Although evacuated tubes can be susceptible to stagnation over time if not used regularly.

Heat Tube Collectors.

Heat Tube Collectors are of a similar construction and appearance to Evacuated Tubes and offer many of the same advantages. Although unlike the Evacuated Tubes, the Heat Tubes are not susceptible to stagnation making them particularly suitable for holiday homes or other properties that are left unoccupied for some of the time. This is because the solar medium does not flow through the tubes. Instead, a process medium evaporates in the copper pipe below the absorber and transfers the heat to the heat transfer medium via a heat exchanger. This means the Heat Tubes have very high system reliability and will work even at very low temperatures unlike a Flat Plate Collector. The heat transferred to the tip of the heat pipe is in turn transferred to a copper manifold in which water (glycol) circulates to heat the cylinder. If a tube is placed in direct sunlight the tip temperature can reach 250°C. The system easily heats domestic hot water to 60°C even on cool days!

Collector Mounting Options

Collectors are best sited on roofs with a southerly aspect. If your property does not have a suitable area on the roof we can mount collectors vertically on walls/gable ends or on a flat roof. We can also mount systems on outbuildings such as workshops or garages or even ground mount. Our surveyor will be happy to discuss these options with you.

Solar Thermal Hot Water Cylinders

For every solar thermal system that is installed a hot water cylinder is required which correlates to the size of the collector on the roof. The average requirements for a domestic home are 100 litres per person. There are two types of cylinder available, stainless steel and copper. A stainless steel cylinder is considerably cheaper than a copper cylinder, although is not as good a thermal conductor as copper and therefore will not transfer heat from the solar fluid to the cylinder as efficiently.

Thermal Stores / Linked Systems

Rather than having a hot water cylinder, it is possible to install a thermal store.
A thermal store is a hot water storage medium/energy system, that can be used for both the heating and hot water requirements for a property.

 It is possible for a thermal store to be linked to either gravity system eg solid fuel stoves/log burners with back boilers, range cookers and stand alone wood or solid fuel boilers. This enables you to use a variety of inputs of differing sizes to their maximum efficiency therefore making them particularly suited to heating and hot water systems incorporating renewable technologies.

 The thermal store can have up to five different inputs to heat the water. These could come from a solar thermal system, a solar PV system, log burners with back boilers. a gas, oil or electric boiler for back up.

Any combination of these inputs could be used to heat the thermal store.

Gemini recommend copper cylinders and stores from McDonald Engineers.

Swimming Pools

Solar heated swimming pools is a one of the best ways to utilise this solar hot water to its full potential. Swimming pools take large amounts of energy to heat using fossil fuel methods. However with solar pool heating you can drastically reduce the heating bills.

 If the pool is not used during the winter months then the solar system could be used via appropriate Under Floor Heating to heat your property!

Other Services

Gemini will inspect, diagnose and remedy any under-performing or otherwise faulty system. We will also service and maintain your system (even if it wasn’t installed by us) to ensure maximum performance throughout its life.

We can lower your energy bills & your carbon footprint, starting today!

For a FREE quotation or more information: