Susan
Isn't 'guys' a gender neutral term too 
I'm a guy, but not Guy :)
[Actuarial] COST/BENEFIT analysis of Solar HWS (in Melbourne) - SKEPTICAL view?
(37 posts) (14 voices)-
GOH
MemberBuzzman
I have a note suggesting 58MJ/kg for [LNG/]LPG. This agrees with your figures.
Your initial cylinder consumption over the last 7 months occurred in the warmer part of the year; and a higher rate of consumption might now be expected.
My older Instantaneous gas water heater appears to be about 80% efficient. (An input of 100MJ/h heats some 13L/m of water by 25C). My measurements seem to confirm this.
With the suburban [Island?] heat effect my climate might not be too different to yours. In winter the groundwater temperature might be around 10C. For a 30C increase in temperature to have a 40C shower at a flow rate of 9.5L/m using gas at 80% efficiency requires no more than 1.5MJ gas per minute. [About 90% of maximum capacity. And you will see that this precludes using both showers simultaneously: or even having a shower-head greater than 11L/m in winter!! However, the home is always relatively warm for health reasons so I don't need excessively hot showers].
About 1.16Wh is required to raise the temperature of 1L water by 1C.
My gas HWS uses a pilot light for ignition. This is specified at 0.3MJ/h - or some 8MJ/d from my ACTUAL measurements. This wasteful operation could provide for a comfortable 5 to 6 minute shower - which exceeds the 4 minute shower per person suggested by our Victorian Govt.
As an aside Wikipedia suggests a GROSS price of $5,000 for Solar HWS in Australia. This seems to accord with others knowledgeable opinions, and might be more for high usage; but in practice family size of 5 or more is likely quite rare - or is so from my recollection of ABS stats.
Posted Sunday 2 May 2010 @ 8:01:18 am from IP # -
IAEA
MemberGOH states......
"I also have some thoughts on the use of off-peak electricity (particularly with our dirty Victorian brown coal) to which I will return later."
This statement of yours was written quite some time ago. When will it be likely that this forum will get to read your thoughts on the subject "Victorian brown coal"?
Cheers,
IAEAPosted Sunday 2 May 2010 @ 12:46:03 pm from IP # -
GOH
MemberIAEA
I'll answer you out of turn.
Thanks for the Cheers but if you knew anything about ME/CFS you would know that a week is not "some time ago"
Months and even years can pass by; but I have had further thoughts on this and hope to spell these out in the next week.PS What does IAEA stand for?
Posted Sunday 2 May 2010 @ 1:12:57 pm from IP # -
IAEA
MemberGOH asks?......
"PS What does IAEA stand for?"
IAEA - http://en.wikipedia.org/wiki/International_Atomic_Energy_Agency
You maye be interested in this? http://www.iaea.org/programmes/a2/
Cheers,
IAEAPosted Sunday 2 May 2010 @ 1:27:00 pm from IP # -
GOH
Memberghostgum
A doubling of water costs
should reduce your payback time
(Shouldn't a Govt be held accountable for IGNORING SCIENTIFIC ADVICE on the adverse impacts of logging in our water catchment areas) ?Could you please recheck the gas consumption figures for the 240L gas storage HWS in your previous home?
I had a 135L gas storage HWS in my prior 2 bedroom unit. Rheem advised me of an average daily storage heat loss of 20MJ - presumably offset by the pilot light running at 12.5 MJ/d. I also have a note that the heating efficiency was only about 75%. [As an aside the dirty (not filtered and even poorer heating efficiency) gas ducted heating had a pilot light that ran at 17.5MJ/day].Even allowing for reduced tank standing heat losses in summer- possibly offset by your larger volume tank- the gas usage seems incredible. (5MJ/day in summer using an instantaneous heater would seem to only allow up to 40L of 40C shower water)?
I sympathise with you on the heavy service provision loading. If usage is not considered commercial on connection you are expected pay the difference up front. NO SERVICE CHARGE SHOULD APPLY. It is a lazy and efficiency distorting way of funding our parasitic business monopolies and DEPENDANT pollies.
Posted Monday 3 May 2010 @ 2:01:52 am from IP # -
ghostgum
MemberGas consumption at that house averaged (over 10 years) for the six billing periods
518, 796 10842, 18116, 12109, 3048MJ.The first figure (518) is for January/February period, and varied from 116 up to 1223MJ.
518MJ for 60 days is about 8.5MJ per day.It was effectively a 2 person household, so two 4 minute showers is about 64 litres of water, so 40C * 64kg * 4.182kJ/kgK = 10.7MJ per day.
Other possible explanations for the low usage would be a faulty gas meter, rusted up cold water pipes causing low flow, and a shower rose that was under 8 litres per minute. I suspect the meter might have been under-reading. The winter energy usage is consistent with a 2 star house.
My parents did have their gas meter replaced after the first winter, when the gas company noticed that the meter appeared to be stuck at 5m3.
Posted Monday 3 May 2010 @ 7:59:44 am from IP #
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