Because of the varying provision of power and energy from the sun, knowledge of the consumption quantities, the consumption profile and the desired hot water temperature is required in the dimensioning of a solar energy system. SolarTron Energy Systems has a calculator for its distributors that shows the amount of solar concentrators required based on water quantity, initial water temperature and desired water temperature. This is an excellent tool for sales people to use because most companies do not know how much energy they use.
In regards to solar concentrators there are two main choices: one axis tracking and 2 axis tracking systems. Systems with one axis tracking concentrate the sunlight onto an absorber tube in the focal line of the concentrator, whereas two-axis tracked system focus the rays of the sun onto an absorber at the focal point. Applications that need water temperatures between 80-90 degrees use 300 million MWh annually in the EU. Which represent 8% of the energy demand? The chemical industry, the pulp and paper and textile industry and the food processing industry consume large parts of this heat.
The advantages of solar concentrators are that they do not get affected by "heat stagnation". In conventional collector systems, if a standstill occurs (for example if no heat is removed or if a component fails) then in order to prevent stagnation temperatures being exceeded, various substantive measures (such as expansion vessels) have to be incorporated. In contrast, solar concentrators > that use tracking systems make use of safety control routines that defocus the collector to avoid exceeding stagnation temperatures. However, suitable safety devices, such as flow indicator, are needed to ensure the flow of heat transfer fluid through the absorber, and thus the removal of heat, before the collector is focused, in order to avoid overheating the system.
SolarBeam uses external heat exchangers. The heat exchangers can be either made from plates or tubes. The heat transfer medium and domestic or heating water to be heated flow past one another in a counter-current. Advantages of external heat exchangers are:
- The heat transfer capacity is higher than for internal heat exchangers
- There is hardly any reduction in performance from lime scale buildup
- Several stores can be charged from one single heat exchanger
Disadvantages of external heat exchangers
- They are more expensive than internal heat exchangers
- In most cases an additional pump is required on the secondary side of the heat exchanger. Therefore they are not an option for thermosyphon systems.
