What would be more energy efficient - solar hot water with natural gas instantaneous booster or heat pump and solar power? What about energy efficiency of instantaneous hot water systems (gas or electric)? Basically, this info is wanted for a small house/hold of 2-3 adults.
energy efficient how water
(10 posts) (9 voices)-
Sunshine
MemberHelenwol,
An adequately sized evacuated tube solar hot water system will need minimal gas or electric boosting, and be considerably cheaper to purchase than a heat pump with solar PV.
Solar hot water is much more efficient than instantaneous hot water systems (gas or electric).We are a family of 3 in Brisbane, with a 30 tube evacuated solar HWS with 315 L tank, and since we have had it installed, haven't needed to use the electric boost yet, even though we have had alot of cloud and rain here in that time.
Posted Wednesday 27 May 2009 @ 10:02:07 am from IP # -
ghostgum
MemberHelenwol, there are figures available for solar + instantaneous gas boost, and solar + storage with gas boost. The instantaneous is more efficient. For the heat pump method, you need to take the solar + electric boost figures, and reduce the electricity consumption by about 1/3 (or what ever the heat pump efficiency really is).
Gas sold in megajoules (MJ). Electricity is sold in kilowatt-hours (kWh). 1 joule is 1 watt for 1 second, so 1kWh is 3.6MJ.In terms of green house gas, instantaneous gas boost is similar to storage + heat pump.
http://www.yourhome.gov.au/technical/fs65.html#designPosted Thursday 28 May 2009 @ 3:08:18 am from IP # -
I have been recording the energy consumption of my Quantum 270l heat pump since installation in July 2006. In the first 3 years it used 4187kWh or 1395.66kWh/year.
Unfortunately it has had to be repaired twice, the first time in July 07 and again just recently. Both repairs have been due to loose connections. Because I have kept regular records I noticed the increases in power use as they occurred and in the most recent problem caught the problem before it became too severe.
Interestingly in the year where I had no problems the average daily use was 3.31kWh/day. So despite the faults it resulted in an increase of only about .5kWh/day average.
I put a bit more of the story and a picture of the dodgy part on my webpage.
Posted Monday 16 Nov 2009 @ 9:44:33 pm from IP # -
dymonite69
MemberThe most energy efficient system may not be the cheapest system. The extra amount of energy saved by the 'best' system over the 'next best' system may not justify the additional cost.
There is also a difference between energy use and cost to you due to differences in prices between electricity and gas. You also need to factor in the efficiency of the appliance.
Solar is the only free energy available to you but only works if you have a good sunny location to put your collector.
Heat pumps are one of the most efficient devices but it relies on using electricity which is generally more expensive than gas.
You could opt for Sunshine's suggestion where it can supply all your winter hot water needs purely on solar. The problem is that you will produce three times as much hot water as you need during summer.
The conventional recommendation is to only have a solar system sized to provide your summer hot water needs and accept that you need to boost during the less sunny times of the year.
Alternatively you look for an appliance that balances the capital expenditure with the energy savings. The money you save doing this might be better used going into other things that reduce your energy bills.
The information that helps you make a choice are:
1) How many litres of hot water are you likely to use per day (average ~ 50L/person/day)
2) Do you have good solar access for where you are going to site the collector
3) What are the energy prices in your area (including if you have town gas)
4) What system you already have in placePosted Tuesday 17 Nov 2009 @ 3:17:52 am from IP # -
The Chief
MemberWhat is the best way to reduce green house gases, using technology?
Solar and heat pump water heaters utilise the suns radiation to directly heat water with around a 75% to 80% conversion efficiency. Solar Photovoltaic power generation is 14% efficient. So actually heat pump and solar water heaters reduce more green house gases then a Solar PV. However PV looks good and it's nice to make something out of thin air!
Saving energy Vs Free energy:
Three solar panels can make about 1.5 kWh /day. Be careful not to confuse this with peak hour solar panel capacity, which is based on a peak hour which is considered to be 1000 watts or 1kWh. A peak hour is based on an optimum radiation level and not the average and as such is not to be used in average power to the grid calculations! Solar panels typically have about 14% solar radiation conversion efficiency and the panels are about 1.5 meter in surface area.For example assuming:
1.5 meter = square panel size
Solar panel conversion efficiency = 14%
2.6 kWh/day average daily solar radiation
Then the daily solar power generated is: 1.5 x .14 x 2.6 = 546watts/day/panel.
Hourly optimum capacity: 1.5 x .14 x 1 = .21 kWh or 210 watts/panel/hourPosted Monday 8 Aug 2011 @ 3:11:23 am from IP # -
Russell Moore
MemberOP is asking about hot water systems, not PV.
I have never used a heat pump, so I can't comment on their real life pros and cons. I have had a flat plate solar hot water heater for 28 years, and have had very little go wrong with it. Yes on cloudy/rainy days we boost, but by and large we don't boost for 3/4 of the year. When we boost (electricity) we do so for about 45 mins using around 2.5kWh. So that is 225kWh+- per year. Our SHWS is on a 16ยบ roof angle, and gets full sun from 9am to 3.30pm minimum every day, we are in Sydney.
Posted Monday 8 Aug 2011 @ 5:50:55 am from IP # -
Sunshine
MemberHeat pump water heaters don't use the sun to heat the water. They use electricity to run.
They just use less electricity to run than a conventional electric water heater. They use same technology as a reverse cycle airconditioner. I disagree they produce less greenhouse gas than solar pv. Solar PV don't use any power to run, other than during manufacture, whilst heat pump water heaters require electricity to run.
Not to be confused with solar HWS and solar PV which run directly from the sun's rays, and don't use any electricity to run.Posted Monday 8 Aug 2011 @ 6:43:16 am from IP # -
Hi Chief, are you really an energy consultant? If true, you must still be a learner. There are too many errors in your post.
You confuse kWh and kW and you use m instead of m^2 (or square meter) and you use 'watts/panel/hour'.
But the worst part is: "...Solar and heat pump water heaters utilise the suns radiation to directly heat water with around a 75% to 80% conversion efficiency. Solar Photovoltaic power generation is 14% efficient. So actually heat pump and solar water heaters reduce more green house gases then a Solar PV. ..." What kind of logic is that?
Posted Monday 8 Aug 2011 @ 8:37:45 am from IP # -
mick_queensland
MemberHi,
also, note that if the solar hot water array is tilted correctly, ie, for winter angle, and it is large enough for your winter requirements, then you will only slightly over produce in summer, and over produce in autumn and spring by about 10%
Cheers, Mick
Posted Monday 22 Aug 2011 @ 2:30:50 pm from IP #
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