The interesting conundrum with solar heating is, the more solar resource is available, the lesser its valued and the lower its requirement. On the other hand, the more one ventures into countries with a colder climate, the more valuable solar energy becomes but its availability decreases. In places like Scotland, one may want to find out if it is feasible to install solar water heater or even a Solar PV panel. Annual insolation level in Scotland are around 800 Watt/m2.
Some people will point out that there are a number of solar companies that are doing successful business in northern European countries. However this fact cannot be taken as a definite proof of the viability. The governments often incentivise green energy generation schemes for a number of reasons. Some of them are as follows:
- To cut down emissions and lower the national CO2 levels
- To help local solar hot water / PV panel manufacturers
- To diversity energy portfolio and improve energy security
- To energize location where grid infrastructure is difficult to laydown etc.
So the number of domestic PV or water heater sales cannot be taken as a measure of feasibility as mostly they benefit from grants or schemes like Feed In Tariff. However, if solar projects are being installed on a commercial basis, than it is a good indicator that the panels are feasible.
For solar water heating, experts have suggested that the mere high demand of heating makes them feasible. Kerr MacGregor, an expert in the field, has suggested that in warmer countries the demand of water heating during summer times plummets whereas in places like Scotland the demand does not drop as much. Studies have suggested that even in low annual insolation countries like Scotland, over 50% of the heating demand can be met through solar water heating alone. It should be understood that heating requirement make up the majority chunk of the energy use in Scotland. 57% of the energy consumed by a household goes into space and water heating. This means that almost 30% of the total energy consumed in Scottish households can be furnished by Solar heating alone.
In the city of Edinburgh, the water temperature for mains water supply during winter goes down to 8 °C. In the summer it can reach highs of 18 °C. Compared to Valencia (Spain), where mains water supply goes up to 30 °C one can notice that in Scotland there is still a margin for heating mains water during summer time. The longer day light hours mean availability of solar radiation is high during summer months, which is also advantageous in northern latitude countries.
It has been ascertained that as far as the requirement is concerned, it is definitely there. It must be now explored if the Solar water heaters are up to the task particularly during harsh winters?
The vacuum tube collector for solar water heating is one of the most efficient renewable energy devices. It can reach efficiency of over 80% in converting sunlight to heat. The vacuum acts as a thermal diode and energy once captured isn’t allowed to escape. Videos on Youtube are available where water with temperature of over 60°C has been extracted from the vacuum tube collector in places where ambient temperature was well below the freezing point.
A conference called the North Sun is arranged every two years specifically for determining novel ways of capturing precious sunlight in high latitude countries. So the answer is yes, Solar water heaters do work in Northern countries. They have been reported to be installed at latitudes of 63 degrees in Norway and are providing value to their users.
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