Additional Questions

1.What are four applications of solar hot water heating?

AnswerDomestic Hot Water, Pool Heating, Space Heating and Commercial process heating (car washes, laundromats, fish hatcheries, etc.)

2. What type of solar hot water systems must be drained during freezing weather?

AnswerOpen Loop or Batch systems CommentThese systems circulate the water that is to be used through the solar collector so there is no way to protect them from freezing. While these systems are mechanically simpler, they will be damaged if they are not drained in the winter.

3. Besides the solar collectors, what component is required for all closed loop solar hot water systems?

AnswerHeat exchanger. CommentThe heat exchanger is what allows there to be a physically separate heating loop in a closed loop system. Heat is exchanged but the fluid in the collector is kept separate from the water that is to be used.

4. What temperature does a solar hot water space heating system operate at?

Answer32°C to 50°C (90°F to 120°F) CommentSolar collectors are more efficient the lower the operating temperature. Therefore, for space heating applications the heat distribution system must be designed with more surface area so that the same amount of heat can be transferred per unit time at the lower temperature.

5. What are the advantages of a drain-back system versus an anti-freeze system?

AnswerDistilled water can be used which is a better heat transfer medium, the system can withstand high “stagnation” temperatures without degrading the anti-freeze solution and the system is fail-safe if a pump fails the system simply doesn’t operate.

6. What is the advantage of anti-freeze over a drain-back system?

AnswerLess energy is required to operate the pumps.

7. What is the most efficient type of solar collector?

AnswerEvacuated tube. CommentEvacuated tube collectors are both more efficient and more expensive. It is important to evaluate the extra cost versus the extra energy when deciding between flat-plate collectors and evacuated tube collectors. Of course, some people think the evacuated tubes look cool, but aesthetic criteria are very different from economic criteria.

8. What percentage of domestic hot water requirements are most economically met by a solar hot water system in Canada?

Answer40% to 50% CommentThe large seasonal variation of solar irradiation in most of Canada means a system designed to supply 100% of hot water in winter won’t be cost effective since much of the hot water produced in the summer will go unused.

9. What size should a pool heating solar hot water collector be?

Answer50% Comment50% applies to an outdoor pool that receives some direct solar gain during the day and with an insulated cover in place at night.

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