Browse Forums Eco Living Re: Solar hot water boost 8Aug 31, 2009 9:32 am Where you are coming from is where you are going to... Re: Solar hot water boost 18Mar 19, 2010 10:37 pm dymonite69 Solarman does make an important point regarding Legionella. There is always the potential for significant exposure although there have been no reported cases of contracting Legionnaire's disease from hot water services. However, even non-solar storage tanks are subject to thermal stratification meaning that not all the water is held at the kill temperature for Legionella. As you draw off hot water, cold water re-enters the tank. Depending on how quickly you consume or when the next boosting cycle occurs, there is always the chance for bacteria to proliferate. In summer, you are generally guaranteed that the tank will be fully heated through in the tank. Heat pumps typically are generally more cost-effective to run in the higher temperate latitudes where there is less solar insolation. However, in the past their capital cost made them less attractive. I am not sure their comparative cost nowadays (given a similar capacity system as solar one). But if you have a large solar system or are a particularly frugal consumer you could considerably reduce additional energy to meet your hot water needs. Finally from a practical point of view of I have tried boost and no boost during summer and the difference is 1kWh vs 0kWh energy used e.g 22c/day. 1kW hr is about enough to bring the temperature of the a 300L tank from 58 to 60 degrees. Generally in summer the tank is going to be way over 60 degrees. Combined with the tempering mixing valve, you are in fact using a much smaller proportion of hot water anyway so you are really left with a reasonable amount of hot water at the end of the day ready to be reheated by the sun the next day. I have tracked my hot water energy use since May last year and correlated it with our insolation and daily temperatures. Here in the Adelaide Hills I could safely switch off the booster mid November to mid February. At a push I could extend it 2-4 weeks either side. Re: Solar hot water boost 19Mar 19, 2010 10:39 pm Thanks Dymonite, you have pretty much confirmed what I said, for 3months of the year your solar can produce far more hot water than you can use – people actually use far less hot water in summer. Your booster will be required for the other 9 months, especially in the middle of winter when the demand for hot water is highest, and your solar provides the least. If you have 3 or more people in your house your booster will use more electricity in those 9 months than one of our heat pumps would use over 12 months. For a more thorough explanation have a look at See http://www.skylineenergy.com.au/our solution.php We use the same technology for hydronic heating systems - much more suitable than solar Re: Solar hot water boost 20Mar 19, 2010 10:42 pm dymonite69 This is the energy loss by a HWS storage tank. HWS efficiency It is about 15%/24 hours. However, note that PV is only around 15% efficient at converting solar energy into electrical energy. Solar HWS vary between 40% (worse) to 80% (best) at turning solar energy into thermal energy. In other words a 300L solar HWS provides as much energy in kWh as a 1.5 kW PV system (3500-3800 kWh/year) That figure of 15% loss is very high . . . ours rate at about 5% the sun master is the solar heating to "warm" the water in the tank the S26 is your hot water system which will heat the water (25 degrees?) so with both turned on you… 2 14203 I want to build a decking to the drawn shape outlined in black. The problem is how close can I build to the gas hot water unit? Will I be able to build around it and be… 0 20349 DIY, Home Maintenance & Repair Hi, I've got a brand new (2nd hand) Bosch Hydropower 16H tankless hot water heater. Since it was installed I have noticed it leaks a lot. I took the cover off and it looks… 0 24293 |