Solar in Summer works well, Heatpumps work well all the time.
Solar/GAS, Solar/LPG or Heatpump OK for domestic hot water!
For domestic hot water: Traditional Solar works great in summer, not so good in winter. The year-to-year Solar gain is roughly the same from heat-pump or solar. If you have natural GAS, the best ecological and long-term sustainable choice is Solar/GAS, but they cost much more to manufacture and install than a Sanden ECO heatpump system.
If you don't have natural GAS, then clearly a Sanden ECO heatpump systems are a better option than Solar/LPG or Solar/Electric - cheaper to buy, install and operate.
Natural GAS or Air-Sourced Heatpump better for hydronics:
For Winter Hydronic Heating Only: Even if you have Natural GAS, a Cold Climate Air Sourced heatpump is best. A condensing GAS boiler is cheaper to install but will cost more to operate over time.
If you don't have Natural GAS, the best option is a Skyline Energy Cold Climate Air Sourced Heatpump.
|NOTE: NEVER BUY A HEAT PUMP WITH AN ELECTRIC ELEMENT IN IT! CHECK FIRST
Lets look at this in greater detail:
For domestic hot water
- Over summer, evacuated tube solar-boosted water heaters can provide more than 100% of the energy required
- Over winter, (and in the colder climates, spring and autumn too), all solar-boosted hot water storage systems will need to run their electric or gas heaters to some extent, virtually every day to ensure a safe water temperature (60oC), to kill bacteria.
- Example: A std. 300Lt storage electric domestic hot water service typically has a 3.6kw electric element
Assuming you use 300Lt/day, it takes 14.6kwh to raise 300Lt by 50oC, so about 4hrs operating - mostly at night
- In the southern states/colder climates, Solar output from a 30 tube solar-boosted evacuated tube system is approx 9kwh to 4kwh/day, so the daily winter average is 6.5kwh/day.
To heat 300Lt by 50oC, the 30 tube solar-boosted electric heater will need 14.6kwh - 6.5kwh =
8.1kwh from the booster (2.25hrs/day operating at 3.6kw)
For Home Hydronic Heating
- In the southern states where home heating is required, heating a 200sqm home in mid winter may need approx. 100kwh/day (equivalent of 2x 3.6kw std. electric water heater units, each running 14hrs/day)
- Given the average daily winter solar output from a 30 tube solar-boosted evacuated tube system of 6.5kwh/day, then you would need about 17x 30tube arrays (about 500 tubes) to be 100% solar self-efficient. (AND sufficient water storage so the energy can be used over 24hrs)
. . . and because solar evacuated tubes produce much more heat in summer, you'd also need to be able to dump 17x 9kwh = 150kw of heat energy every day in summer! - 300-500 Solar tubes is just not practical or cost efficient.