Green light for solar hot water

Jim Sebastian.
[More Images]

Sebastian says the boom in construction, especially high-rise and villa developments, has placed an extra burden on electricity generation, as all these have electric water heaters. “We are urging customers to install solar water heating systems, and thereby save up to 75% of the connected electric load.” Another problem is that while consultants may be aware of the technology and its potential benefits, “when it goes out to tender, it often gets sidetracked in value engineering.”

However, the latest trend towards building efficiency has placed the spotlight firmly on solar water heating as a cost-effective option to realise immediate savings.

In addition, Solahart products are particularly suited to the region’s harsh climatic conditions, when some similar European products are known to have overheating issues. “Solahart has a presence in 90 countries, and has been manufacturing solar water heaters exclusively since 1953. Its technology is characterised by the drainback principle, whereas most other manufacturers utilise fully-flooded systems. “What happens normally is that most people place everything on the roof, which means the circulating fluid is always in the loop, the temperature goes too high, and then the pumps and pipes fail. Our system is very simple, as it switches and drains back off before it can overheat,” explains Sebastian.

In addition, the collectors comprising the system are extra strong and durable. Solahart has six different collectors, depending on the specific requirement. “We install and commission the systems on a one-stop shop basis from design to installation. We even assist in calculating the total hot water requirements, the number of collectors and what back-up is needed, as consultants are normally so busy.”

The average lifespan of a Solahart system is anywhere from 12 to 25 years, depending on routine mechanical equipment maintenance. “We have a maintenance contract with Holiday Inn, for example, whereby we supply technicians and ensure that the systems are running properly.” Sebastian says that one particular Solahart system reloca- ted to the company’s head office in Australia had been in operation for an astonishing 50 years.

Story continues below

Advertisement

FEATURED COMMENT I would appreciate if cost comparison both capital and operating justifies hot water through solar instead with steam fo   1 Comments Read more comments »

Solar power encompasses both solar thermal and solar PV. Firstly, efficiency is much higher for solar thermal. Up to 80% of the sun’s energy can be exploited with a thermal solar collector, whereas with a PV collector, sunlight-to-electricity conversion rates average about 12% to 16% only.

The rule of thumb is that the energy available from the sun is about 1 kW a square metre. This is equivalent to 3 412 BTU/h/square metre. Therefore if you can get 80% efficiency using a solar thermal collector, you would only need about 37 square metres to generate 100 000 BTU/h, or the amount of heat generated by a typical gas furnace.

Thus a solar thermal system would require much less space (and many fewer collectors) than a solar PV system. Not only that, but solar thermal collectors are about five times cheaper than solar PV panels. So you have a scenario in which you have a system that is six times more efficient at 20% of the total cost of its rival. How then can solar thermal not be dominating the solar industry?

Of course, it is not quite that simple. For one, heat is difficult to store without a thermal mass.

Passive solar homes will likely incorporate thermal mass walls (that is, concrete or other masonry) to store collected heat. Yet this can only be achieved via a passive solar design, starting at the home’s conception. It is difficult to add thermal walls and other passive solar collectors to an existing home. Therefore, when retrofitting a solar thermal system, you will have to use an active system, which uses a transfer fluid and a large water storage tank.

Furthermore, you will need to calculate the intensity of the sun at different times of the year. In addition, because of clouding, you may need to have a back-up system also. All these complications and distributed yet fast-accumulating costs may be why solar thermal space heating is still more possibility than actuality.

Another big advantage for solar PV is that it is usable year round. A solar thermal space heating system will sit idly by during the long summer months while a solar PV system will provide usable electricity all year. The system would be at its most efficient just when you need it most.

However, solar thermal is said to represent the future of solar energy and a ‘green’ electrical grid. There have been new innovations in thermal storage techniques, if only practical on a commercial scale at the moment. For the residential homeowner, a solar thermal hot water system can result in quick, tangible savings, especially as hot water is the second most consumptive energy user in a home.