Evacuated Tube collectors use the vacuum to stop any loss of heat energy from the system through conduction. Flat plate collectors will always lose some amount of energy via conduction, whilst the vacuum in Evacuated Tube Collectors mean there is virtually no conduction losses. Flat Plate panels will always be affected by the outside/surrounding air temperature, no matter how good the insulation around the panel is (or even if the glazing on the top is double glazed). Indeed, an evacuated tube collector will produce almost as much energy on a sunny winter’s day with outside temperatures of 0 degrees Celsius as it will on a sunny summer’s day with outside temperatures of 20 degrees! You can see how a panel’s efficiency changes when the panel’s temperature rises above the outside ambient air temperature in the following chart:
Note that the temperature of these panels can often exceed 100 degrees Celsius at times. In tests conducted in the UK, results have shown that a meter squared Evacuated Tube panel can produce approximately twice what a meter squared Flat Plate panel will produce. The annual production levels of each panel can be seen in the following chart, which also shows the annual demand for Domestic Hot Water in a typical UK household:
However, some will argue that Flat Plate panels perform better in very cold and snowy conditions, as the temperature of the panel will melt any snow or ice that comes into contact with the panel. This is indeed true, but given the UK climate it actually counts for very little. Similarly, some argue that Flat Plate panels produce more energy in the summer months. Again this is of little relevance as both panels produce enough energy in the summer months to satisfy the DHW demands and thus any production above and beyond this is simply wasted or dumped!
However, Evacuated Tube panels are more expensive! A typical Flat Plate system can cost as little as £3,000 fully installed, whilst an Evacuated Tube system will cost around £4,000 fully installed – a significant percentage increase.
Home Pages of interest:
- Visit the Solar Thermal home page
- Visit the Energie Solar home page
- Visit the Solar Thermal and Swimming Pools home page
Other Pages of interest in this section:
- What is Solar Heat Power?
- How Does Solar Thermal Work?
- Types of Solar Thermal Systems
- Flat Plate versus Evacuated Tube Collectors
- Annual Energy Production
- Components of a Solar Thermal System
- Costs of a Solar Thermal System
- Servicing and Warranty
- Solar Thermal Financials and Paybacks
- Our Products
- Solar Thermal and Swimming Pools
