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Author Topic: GSHP versus ASHP  (Read 16308 times)
dhaslam
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« Reply #45 on: February 10, 2011, 12:28:30 PM »

Heat pumps should  only use  off peak electricity, otherwise there isn't  much advantage other than  saving  fossil fuels by using renewable sourced electricity.  
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titan
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« Reply #46 on: February 10, 2011, 05:39:06 PM »

Heat pumps should  only use  off peak electricity, otherwise there isn't  much advantage other than  saving  fossil fuels by using renewable sourced electricity.  

It depends on the situation. My calculated heat load is around 15,000kWh  and estimated normal usage around 3000kWh. With a heat pump the actual heat demand with a COP of 3 is 5000kWh put these figures into a power comparison site and because of the high day tariffs with off peak ,  25.14p and 4.97p the difference is small. You can fiddle with the figures, standing charge, no standing charge etc but the principal remains unless you have a high off peak demand off peak is quite often not the best option. There is also how best to use the off peak power, my floor may hold enough heat to last all day or maybe I could use a large thermal store but with high levels of insulation and low flow temperatures the heat demand may not be high enough make off peak worthwhile.
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baker
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« Reply #47 on: February 10, 2011, 08:25:21 PM »

 
Hi a thought
geothermal ground horizontal heat pumps are at rated output at brine 0c
when the demand is on and the loop temperature drops,  the cop also drops. the output drops,and power con sumsion may increase if inverter technology
the soil conditions and
the climate also has a influence
so calculations most of the time guess work if working with the factory test conditions
the energy bills will increase as the season progresses
john
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titan
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« Reply #48 on: February 10, 2011, 10:44:41 PM »


 calculations most of the time guess work if working with the factory test conditions
the energy bills will increase as the season progresses
john

There are plenty of independent reports showing GSHPs when installed and operated correctly give COP figures similar to the EN 14511 manufacturer test figures.
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billi
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« Reply #49 on: February 10, 2011, 11:50:36 PM »

for the time beeing  my opinion is to  raise  electricity costs per unit  for heating
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« Reply #50 on: February 11, 2011, 08:33:31 AM »

for the time beeing  my opinion is to  raise  electricity costs per unit  for heating

And the logic behind this opinion is ?
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baker
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« Reply #51 on: February 11, 2011, 09:53:01 AM »

 Hi
I have called to many heat pumps with horizontal ground loops
and have never see 0c in the latter season  maybe its because they were not installed correct
and i see all the problem installs,which makes sense
 can i ask anyone out their if you can recall
what was  the average temperature in their horizontal ground  loop in the latter season
 the temperature on the ground loop return/ inlet when pump running for 4 hours or more
thankyou

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billi
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« Reply #52 on: February 11, 2011, 10:21:39 AM »

Quote
And the logic behind this opinion is ?

..... that i have my reservations , that too much support like RHI for heatpumps and it is too early   that we can focus to shift our energy consumption towards electricity  and (H)eat a big proportion  of the Renewable electricity units supported by FIT 

A COP under 3  as far as i have read  can not  be called climate friendly

Billi
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qeipl
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« Reply #53 on: February 11, 2011, 02:04:56 PM »

Quote
And the logic behind this opinion is ?

..... that i have my reservations , that too much support like RHI for heatpumps and it is too early   that we can focus to shift our energy consumption towards electricity  and (H)eat a big proportion  of the Renewable electricity units supported by FIT 

A COP under 3  as far as i have read  can not  be called climate friendly

Billi

Billi,

If not now, when?

We need to be doing everything, now - installing heat pumps, developing renewable electricity generation, and insulating/draught-proofing on a massive scale.

Even if we get a bit ahead on the heat pumps, burning gas to make electricity to run heat pumps in properly insulated buildings is more carbon efficient than burning gas in domestic boilers in averagely insulated buildings.

We get confused by people who tell us that electricity is 'high-grade' energy and shouldn't be used for heating.

When oil and gas become scarce and expensive electricity will be the only viable source of heating energy (additional to the sun) for the mass market - we will all be using electricity.

Heat pumps are far and away the most efficient use of electricity for heating because they are adding local solar energy to the electrical energy that they consume.

We must promote the development and use of heat pumps now so that when the crunch comes we already have a good base load of installations and new, improved models coming to market.

Rant over.

Malcolm
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billi
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« Reply #54 on: February 11, 2011, 02:44:00 PM »

Sure i understand that heatpumps are playing a big role and are generally fine in my opinion

But  there should be a setpoint    of COP  agreed  for heatpumps  that will receive  financial help,  as well if the house  and the existing system is fine to run a heatpump

It does not make sense to me to  support heatpump ideas with a lousy COP the same way like units with COP of 4-5

And  consequently  one could ask why one that installs a gas boiler is not getting payed , cause he heats his house more environmental sound than with a inefficient heatpump

Billi







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1.6 kw and 2.4 kw   PV array  , Outback MX 60 and FM80 charge controller  ,24 volt 1600 AH Battery ,6 Kw Victron inverter charger, 1.1 kw high head hydro turbine as a back up generator , 5 kw woodburner, 36 solar tubes with 360 l water tank, 1.6 kw  windturbine
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« Reply #55 on: February 11, 2011, 09:02:02 PM »

Billi,

The graph on this page suggests that a heat pump with a COP as low as 2, run on electricity from a gas power station, will be more efficient than a domestic gas boiler running at 90% efficiency.
http://www.inference.phy.cam.ac.uk/withouthotair/c21/page_150.shtml

I'm guessing that my ASHP runs at a COP of between 2 and 3 for the times in the year that it's running the UFH without any input from the wood boiler. (It'll be doing 3 or 4 in the summer for DHW).
It may be 'lousy' but it's still producing less CO2 than if I had mains gas and a condensing boiler, and lots less CO2 than the oil/LPG/coal/raw electricity alternatives that are available here.

As for incentives, I confess that I don't understand the logic behind the RHI.
Surely we should be incentivising insulation, triple glazing, and the like - reducing the demand for heat - before we encourage people to install heat pumps and pellet boilers.

Maybe the first 500 units of electricity per month should cost 3p/unit and everything thereafter should cost 50p/unit.
At the same time we should grant aid insulation etc. - the installer (tradesman or DIY) gets the grant when the house passes a heat loss test (like Ivan's thermal image thing, maybe?).
Then put zero VAT on heat pumps, pellet boilers, etc. and let the rising gas prices gradually drive people away from gas boilers.

Malcolm
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Our Money: how to shrink government, boost business, eliminate poverty, and make the economy work properly for everyone.

A book for people who are perplexed about the economy.
Available from Amazon in paperback and eBook.
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