[EdwinSm]

Can you help me with some information - namely the average amount of oil equivalent that is used to produce a kWh of electricity in oil fired or gas fired powerstations?

The organisation I work for has installed a ground heat exchange system to replace an old oil furnace. They have two more properties that could have the same change, and I want to encourage them to carry on with energy conservation (especially as most of the oil used here comes from Russia ).

It is too early to get really accurate calculations of the energy/money saving, but the first results look positive (although slightly less than first anticipated).

The cost savings look substantial - the extra electricity cost is only 32% of the cost for the oil (average volume over 13 years).

I was wondering what that actual energy savings cost (this is for my own interest and probably will not be included in any 'encouragement' to the firm).

From the internet I have found that 1 kg oil equivalent = 11,63 kWh
and that heating oil has a density of around 880 kg/m3.

With 24 900 liters of oil saved (equal to 2+ small road tankers) this works out at the equivalent of 257 700 kWh. The extra electricity used is just below 70 000 kWh - so in energy terms the new system only uses about 27% of the energy of the old systems.

However, as there are inefficiencies in electricity production and distribution, I was wondering what factor I should add to that 27% to get nearer a true figure. Also I am wondering if the cost is a good proxy for that inefficiency (indicating a 18-19% inefficiency), or if there is some anomaly in our local pricing systems.

[Pops]

This handy graphic shows 68% of oil energy is lost in production.
http://www.theguardian.com/news/datablo ... -politics#

I left it big:

[EdwinSm]

Thanks Pops!

68% - OUCH

Plugging that figure in the result is if the extra electricity is generated by oil or gas then the new system is saving about 60% of the energy formally used. Still very worthwhile for the 'down slope' after peak oil, but not too much help when supplies of fossil fuels are very limited.

The figures also help illustrate that the prices in Finland for electricity are low (at least by the European standards). A fair amount is hydro (including imports from Norway and Sweden) so I suppose that helps lower the costs.

[hvacman]

It's unfair to make a decision about what a new electrical device's economics/energetics might be based on current fossil fuel power plant efficiencies, especially fuel oil plants, which are increasingly rare and obsolete.

Think 20-30 years. Invest in a new oil furnace and it will burn....oil....to make heat for the next 20 years. Maximum fuel efficiency = 0.95 BTU heat out/BTU of fossil fuel heat chemical energy in.

Invest in a new electric ground source heat pump and it will burn...oil....hydro...solar...wind....natural gas....coal...nuclear...biogas....wood chips....etc. etc...to make heat over the next 20 years. Think of electricity as an energy currency, not an energy source.

When you look at the typical gshp Coefficient of performance (heat energy out/energy in) = 4.5, heat pumps can leverage state-of-the-art fossil fuel power plant energy. For example, CCGT (combined cycle gas turbine) power plants can achieve 60% net thermal efficiency. Assuming 8% distribution losses, that means 55% of the fuel energy is available to the heat pump electrical connection. Multiply 0.55 x 4.5 = 2.47. This means a GSHP turns one BTU of natural gas chemical energy into 2.5 BTU's of heat. With those types of leveraged heat output numbers for heat pumps, it makes no long-term energetic sense to burn natural gas, or any fossil fuel, purely for heat in climates where heat pumps will work.

Even if GSHP's become costly due to the cost of the ground bores, the new inverter-driven air source mini-split heat pumps give a substantial energy heat leverage. They have a seasonal average COP of 3.0 and even in zero degree F weather the new high-heat units have a COP of 1.8.

[EdwinSm]

It's unfair to make a decision about what a new electrical device's economics/energetics might be based on current fossil fuel power plant efficiencies, especially fuel oil plants

Agreed... the main decision was a financial one - the old boilers were over 20 years old and needed replacing. I suppose I was just interested in what the actual savings might have been in energy terms, and what it might mean in terms of imported energy, and comparing it with a fuel oil plant was the 'worst case'.

While the air heat exchange systems work well, they are not very good when most needed, that is when the temperature gets down to -20 C. However, for smaller buildings, a air heat exchange combined with a good wood burning stove is (in my opinion) a very good option for where we are living.

For my own house the decision was more 'peak oil' driven, in that when we bought our house the oil furnace was about 24 years old, and I wanted to move away from oil. So I went for a ground heat exchange pump to replace it, with supplementary and backup heating from a wood burning kitchen stove. The payback period was a long 8 or so years, but I have found it worthwhile (especially now that I am loosing my job and the fuel costs are much much lower than they would have been otherwise). I have found that as I have planned for the effects of Peak Oil realistically with the infrastructure that there is, all I can do is plan for a transitional period with lower energy input. To plan for a time of almost no fossil fuel, I would need to build a new house, with this goal in mind.

[Pops]

Thanks hvacman, good info.

Can you give a guess at an average installed cost for such a system in a moderate climate?

[Subjectivist]

Thanks hvacman, good info.

Can you give a guess at an average installed cost for such a system in a moderate climate?

Well a year ago my wife and I got an estimate for a ground source heat pump because I am an efficiency nut. Unfortunately we do not have a large pond or a river on our property to use so they would have to drill a number of exchange wells lined with copper pipe around our ranch style house. The energy costs would be 1/3 of our older natural gas furnace and 1/2 of our old central air system, but installation would be $18,000.00 compared to about $8,000.00 for a new gas furnace/air conditioning combination. There is a $3,500.00 tax rebate for the ground source heat pump, but it still prices out about twice the installed cost of a traditional system.

We decided to wait a year and see what prices might do, but it was a hard winter around here and we kind of regret the delay.

[Pops]

Yeow. Thanks Sub.

Now put $40k of PV on the roof, by a PEV for another $40k and yer set for 20 years or so.

[Subjectivist]

Yeow. Thanks Sub.

Now put $40k of PV on the roof, by a PEV for another $40k and yer set for 20 years or so.

After I win the lotto lol! Signed the contract for new furnace and central air last night, 96% efficient gas, 16 SEER a/c. $8,800 for this conventional system, the ground source heat pump last year was $17,790 and went up to almost $19,000. Th old system is a 1994 furnace and 1989 central air so energy savings should be substantial.

[hvacman]

GSHP's are really cool, and horrendously expensive - we see $10/foot and up for vertical bores here in CA, with about 250 feet/bore and 1 bore per ton (exact length depends on the underground geology). So that means $7500 for just the bores for a 3-ton unit that can create 36,000 BTU/hr. Add another $10,000 for the 30 SEER GSHP unit, pumps, connecting piping, and ductwork and you're at about $17.5K.

FYI, we used to get much cheaper GSHP drilling costs when gas/oil was cheap. A lot of the GSHP bore drillers 14 years back were former oil/gas drillers who were looking to stay busy when no one was drilling for oil. Those days are long-gone.

If you have a lot of land that's easy to dig, you can try horizontal ground loops. Dig 1000's of feet of 10' deep trenches and drop in the pipe. Efficiencies aren't as good, though, as ground temperatures fluctuate a lot more at 10' deep than at 250' deep.

The high cost is why, for moderate climates, the mini-split air-source heat pumps are really catching on. Installed cost is more like $6K-7K for 3 tons of 22 SEER units. No bores, no pumps, no pipes other than the short refrigerant lines. It will use about 25% more electricity, but just spend another $3K on more weatherization and it becomes a push.

In really cold country, GSHP's still are the efficient heat pump of-choice, as they are the only system that can keep on cranking out efficient heat after days and days of -20F temperatures.

[PrestonSturges]

I'd like to see numbers for a GSHP for my area. In a one mile circle around me there are four lakes of about 10 acres, and historical homes had hand dug wells. Ground water is probably no more than 30 feet down. It's not an aquifer, but I think i could get all the GSH I need. However, the systems which people discuss always involve going 300 feet down for the Perrier.

[Subjectivist]

I'd like to see numbers for a GSHP for my area. In a one mile circle around me there are four lakes of about 10 acres, and historical homes had hand dug wells. Ground water is probably no more than 30 feet down. It's not an aquifer, but I think i could get all the GSH I need. However, the systems which people discuss always involve going 300 feet down for the Perrier.

If I recall correctly a pond of as little as a half acre in surface area at least 20' deep is all a typical house needs as a source and sink for geothermal exchang systems. Water has a huge heat capacity and that volume of water is all you need as it absorbs heat from the soil below and around it in the winter, and dispells heat into the air above in the summer. Here near Toledo, Ohio I live on a large lot but much less than an acre and with no natural water access so the only option would be vertical wells.

[hvacman]

Pond-based GSHP systems are very site-specific. In Plumas Co. in CA's Sierra Nevada mtns, they have quite a few GSHP systems with ponds. Because it gets so cold in the winter, the ponds freeze over every winter. They don't need much air conditioning in the summer, so the AC doesn't help the ponds warm up again. If the pond is too small/shallow, some smaller ponds never really warm back up sufficiently, slowly getting colder each year until the surface ice gets so thick by early spring that the ponds haven't really thawed out until late summer. We know what the albedo effect for the Arctic ice cap is all about. The same applies for frozen ponds. They don't start warming up until the cover ice thaws.

This can also happen with vertical or horizontal bores if things aren't sized properly for the total year-round heating and cooling load of the specific building at a specific location. The ground can overheat after a few years in a cooling-dominated climate or start to freeze up, even if it is 200 feet below the surface, in a heating dominated climate, if the bores are too small, too few, or too close, below-ground geology, what is used to backfill the bores or trenches, presence/lack of ground-water, etc. GSHP's borefield or pond-loop sizing can be a complex science.

If the ground is really saturated just 30' down and it is any sort of aquifer where the water is slowly migrating laterally, that can be a pretty good GSHP source for some shallow pipe loops. The slowly moving water will keep the ground at a constant temperature and "sweep" the heat or cold on down the line, or you could make a "direct water source" type system and install a single a shallow well and pump the water up to above-grade to extract the heat, then re-inject it back down in a disposal well. Again, an experienced GSHP designer can figure out what might work at your site, but it takes more than just a rule-of-thumb.

[Keith_McClary]

Considered GSHP when building house in Alberta 7 years ago. Decided against it because a neighbor had problems drilling through alluvial boulders. As it turned out, given the relative costs of NG/electricity and furnace/GSHP, we are much better off with NG. So far. As for environmental/AGW issues, our electricity is coal generated.