Domestic Solar Heating

Get up to 70% of your hot water needs from FREE solar energy- and do your bit to save the planet whilst saving on your bills.
Barilla offer a range of options for domestic solar heating systems- either Evacuated Tube or Flat Plate collectors, on a pitched roof, in-roof, or on a flat roof.
Our Kingspan Varisol tubes are the most efficient and technologically advanced renewable product available anywhere in the world. The HP model features a patented heat limiting mechanism which solves reliability issues associated with over heating. 
The domestic RHI (Renewable Heat Incentive) of 20.06p/kWh paid for 7 years, along with the planet benefitting from the CO2 savings and the homeowner saving on their energy bills, gives a solid return on investment.

Benefits of using Solar Heating:

These are the main benefits to the domestic user:
  • Uses clean renewable energy source
  • Reduces your fossil fuel consumption and hence CO2 emissions
  • Save money on fuel that you would have otherwise needed to purchase
  • Enhance the life of your boiler by reducing the amount of switch-on / offs   
  • Low maintenance technology
  • Integrates with existing heating or other renewable sources
  • Solar Heating is backed by Government incentives to reward consumers who invest in green technology
  • Low cost and simple way for you or your company to contribute towards tackling climate change

The amount of money and CO2 that you save will be dependent upon your consumption, the fossil fuel type that you are replacing, and the energy efficiencies of both your building and boiler.

How Solar Heating Works

Global irradiation - The "fuel" of a solar thermal system

Solar thermal collectors make use of the energy contained within radiation that the Earth constantly receives from the sun. This radiation takes the form of both visible and invisible light across a wide spectrum. The radiation that is received at the outer surface of our atmosphere is termed solar insolation, and once it has passed through the atmosphere the radiation that we receive at the Earth's surface is called global irradiation.  It is this global irradiation that "fuels" the solar thermal collector.

Global irradiation can be broken into two main components; direct and diffuse radiation. Direct radiation is received on the earth's surface with no interference from the atmosphere or clouds. Diffuse radiation is dispersed by the atmosphere or clouds before reaching the earth's surface. In Northern Europe the average percentage of diffuse radiation as a proportion of global irradiation is about 50% over a year, this figure is higher in the winter and lower in the summer.

Nearer the Equator this diffuse proportion can be nearer 20% of the total. The high level of diffuse radiation in Northern Latitudes has had an impact on collector design and in particular the proliferation of Evacuated Tube Collectors which are optimised to work in diffuse radiation.

Another factor that affects how much radiation that the earth's surface receives is how far it has had to travel through the earth's atmosphere, this reducing effect is known as air mass. If radiation hits the earth's atmosphere perpendicularly (Air Mass Index = 1), then it travels less distance through the atmosphere than if it hits at a more acute angle (Air Mass Index = 1.5). This effect will be seasonal and latitude dependent.

Solar Collector - Absorbing the radiation and generating heat

A solar collector works by transferring the energy contained in the solar irradiation into heat energy. There are two principle designs of solar collector; the Evacuated Tube Collector and the Flat-Plate Collector. Both these types of collector integrate in a solar circuit in the same way but their designs are radically different.

Evacuated Tube Collector

Heat Pipe Collector

An Evacuated Tube Heat Pipe Collector is made up of a series of glass tubes containing heat pipes which can be modular (Kingspan Varisol) or the more traditional fixed manifold option where the tubes "plug-in" to a manifold. Solar irradiation is received by the tube and absorbed via a coating on the inside of the glass, this coating becomes hot and transfers heat energy through an aluminium foil to the copper heat pipe. Within the copper pipe there is an aqueous solution held in a vacuum that is allowed to rapidly boil and condense in the heat tip. The energy generated in the heat tip is then transferred to the solar circuit via the collector manifold.

Flat Plate Collector

Flat Plate Collector

A Flat Plate Collector has a large glass cover, an aluminium absorber plate and a copper pipe register. The higher performance and quality flat plates, such as the Kingspan FPW series, use anti-reflective glass to allow higher levels of irradiation to be absorbed. The absorber plate is heated and transfers energy to the copper pipe register attached to the back of it, fluid from the solar circuit is heated by circulating it through the copper pipes.

Solar Circuit - Utilising the heat that's been generated

Schematic of Solar Thermal System

Whether you chose a flat-plate or evacuated tube collector you will require a method of utilising the heat that the solar panels have generated, the diagram above shows a typical circuit that is capable of doing this. The main components in the circuit are a solar collector, a pump station and controller, an expansion vessel and a twin coil cylinder. The solar circuit is sealed and contains a solution of water / Propylene Glycol which is used as the heat transfer medium and for freeze protection. The controller is used to monitor both the collector and cylinder temperatures, using a sensor probe mounted within both items, as the temperature in the collector rises above the temperature in the base of the cylinder a pump is activated and the heated fluid in the collector is circulated through the solar coil in the cylinder. This process is repeated in steps until the cylinder reaches its maximum temperature, typically 60°C. 

The purpose of the expansion vessel is to allow for the expansion of the fluid in the sealed system as it heats up. The discharge container, shown alongside the expansion vessel in the diagram above, is designed to capture any fluid that may released from the system via the Pressure Relief Valve attached to the pump station.