Solar hot water systems have been fitted in the u.k since the early 1970's'.
Up to to 2006 it was estimated that there was going to be 2 square metres of
solar panel installed per 1000 people. That is about 120,000 square metres.
Solar can be incorperated with other fossil fuel heat sources to help reduce
the amount of carbon emissions and to slow down the use of our ever
depleting fuel resources. A typical solar hot water system can contribute up
to 70% of your hot water heating requirements.

There is an average 1000 watts of energy from the sun per square metre at
ground level. So if we took into consideration a 4sq.m solar panel
installation with a collector efficiency of 70% then the system would
generate about 2.8 kw of usable energy for hot water at peak time.

Types of Solar panels - Flat plate collectors

Like all the panels it consists of an absorber plate.Small copper pipes run
up and down the plate taking heat from the absorber to the glycol fluid
within the pipes. The most common materials are copper, copper-alluminium or stainless steel, due to their high conductivity.

There are two types of coatings applied to absorber plates, selective and non-selective. Non-selective can absorb 90-95% of the energy but also can emitt up to 90% of the energy it has recieved.

A typical example of this is matt black paint. The other and more widely used coating is selective this is due to its low emmitting properties and can result in a 20 - 25% increase in the energy collected per sq.m per year.The panels are insulated at the rear and sides to increase efficiency and they are glazed at the front to allow maximum energy to enter the panel and to decrease the heat loss within.

A glycol fluid is circulated directly through the panels to absorb the energy from the sun and transfer it to the hot water cylinder. Flat plate collectors are popular due to their aesthetic properties. These type of panel can be fitted on the roof or integrated within the roof tiles.

Evacuated tubes

These type of panels can be devided into two categories- Heat pipe- This takes advantage of the thermal properties of a volatile boiling liquid to transfer large amounts of heat. It is a copper tube containing a special fluid which evapourates when the suns energy hits it.

Once the heated vapour rises to the top into a condenser located in the the primary water within the manifold. Once it has transfered the heat to
the system water is then cools and flows back down the tube to have its cycle repeated.Due to this effect it has a thermal conductivity many times greater than a solid metal like copper.There is a vaccum within each glass tube which eliminates any convection and conduction losses from the
absorber. Between 10 - 30 tubes can be assembled into a manifold, of which
carries the primary fluid(Glycol). The manifolds are insulated and weather
proof to increase efficiency.

Primary fluid design- These types of tube have the same vaccum as within the
Heat pipe, but they actually circulate the primary fluid down the tube and back up into the manifold. These are more efficient than the flat plate but not as effective as the Heat pipe design.

Solar for swimming pools- There are two types of solar heating for swimming
pools.

• Heating the pool water indirectly through a solar heat exchenger with either flat plate or evacuated tubes. A typical system would need about 11 sq.m per 20 tube 58mm evacuated tube panel
• The actual pool water is circulated through black plastic panels situated
  on a roof or floor mounted on A frames. A typical system with these panels will need to be 50% of your pool surface area.

Solar assisted underfloor heating

With a solar underfloor heating system you can cover 30% of your space
heating requirements. This is acheived by using one of our specially designed thermal stores. When the temperature of the solar panels are higher than the temperature at the bottom of the thermal store then the integrated pump circulates the sealed glycol fluid from the panel and through a heat exchange coil within the store. This transfered heat can then be circulated through the warm water underfloor heating in the house at about 35 degrees. Therefore with this flow temperature even the cloudiest of days can make an impact on your heating. The principle of underfloor heating is to heat a thermal mass i.e concrete of which holds the heat within the screed. Concrete has a good specific heat capacity and can store heat for long periods of time. Our expert engineers can design a system for your individual requirements. The thermal store size will be sized dependant on the size of the house and how many solar panels we can install on a south facing roof. Solar space heating panels requires a steeper gradient in comparison to solar domestic water heating this is due to the sun being lower in the winter. We usually specify a 55 degree inclination. For further
information you can send us your project plans and requirements and we can
design a system to suit your needs.

View Movie file

Is my roof facing the correct way?

You ideally need a south facing roof but there are other applications like
east-west systems where we install a panel on the east and the west roof.

How much saving will I get from my solar hot water system?

You can generate all your hot water through the summer months and 30-40%
through the winter. So over the whole year you could generate up to 80% of
your hot water through solar.

What size solar hot water cylinder do I need?

As a rule of thumb you work on the basis of 50 ltrs per person per day and 1
sq.m of solar panel per 50ltrs of water. Example- for a house with 4 people
in you instal a 200ltr hot water tank with about 4 sq.m of panels.

UK solar irradiation
Annual Total kWh/m2

Fig 1.: map showing average solar radiation on a 30° incline facing due south.

Fig 1 shows the total average solar radiation falling on one square metre surface inclined at 30 degrees to the orizontal, measured in kilowatt hours.

These figures bring out the remarkable fact that the amount of solar energy
falling on the total roof area of an average house is many times that
required to provide all its heating and hot water.

However, we must note that there is a large difference between the radiation
available in the summer and that available in winter; also Active Solar Heating systems will typically convert 40 to 50% of the solar energy falling
on the solar collectors into useful heated water. These factors must be
taken into account in determining the optimum size for a system.

The illustration shows a typical Active Solar Heating system layout. An electronic controller constantly compares the temperature of the solar collectors with the temperature of the water in the cylinder.

Whenever the collectors are hotter than the cylinder, the controller switches on the system's circulating pump. A mixture of antifreeze and water is then circulated through the collectors and the cylinder's heat exchanger, heating the cylinder in just the same way as a central heating boiler.