Topic: The myth about "free electricity" in winter - page 3. (Read 9365 times)

If you meant why these systems cant work autonomously; in order to produce electricity you have to make water boil. to achieve that kind of concentration of heat and achieve a positive energy return, you need large and expensive devices and large enough temperature difference. Like those geothermal generators linked above; they exist and they do produce electricity, its not impossible, but its not really something thats economically feasible in a house

Thats more or less what these devices do. But since it costs energy to compress and decompress, the energy is not free. But you can get > "100%" efficiency if you measure efficiency as electricity you spend for heat inside your house. You will be cooling the outside world a bit though (or warming it if you are trying to cool your house).

But if you can use room temperature to make the air hotter, why can't you use that generated hot air to power your air heating device?

YOu are harvesting heat stored outside or in the ground (geothermal). If it helps you understand, imagine living in iceland next to a hot water well and pumping that water through your house. You would use a few 100W in electricity to pump the water but you would obtain a 1000x more in heat.  Doesnt violate any thermodynamic laws.  You just need a source of heat, and with a heat pump, even fairly cold outside air or water can be used as a source of "heat". All you have to do is cool your inside air to a point well below that of your heat source (by compressing it), then heating it up, and decompress it. IOW, all you need is a temperature difference.


Oh and yes, you could use that to generate electricity too, if the temperature difference is big enough. Its already done:
http://en.wikipedia.org/wiki/Geothermal_electricity

uh yeah people have seem to forgotten the law of conservation of energy..

Could someone please explain to me how somthing can be more than 100% efficient without allowing people to use its output to power the device for free?

This post only applies to those with a card or three.  It's 26 degrees (F) outside currently and the air exiting my "mining room" is a nice 72 degrees.

Not everyone has *your* climate.     It takes a *LOT* to keep a house heated here in the winter.  With my mining rigs going, I haven't had to touch the furnace.

Consider both mini split systems (which have install cost) as well as window heat pumps which do not if you can put them in the window/wall yourself. 

http://www.ebay.com/itm/LG-LW1210HR-12-000-BTU-Window-Air-Conditioner-heat-/160558003778?pt=Air_Conditioner&hash=item256200b642

I am not recommending this specific unit, but this gives you an idea of what is out there.  I have an 18000 BTU heating/cooling one.  These can pay off vs electric heating in less then one heating season because they are 2-4x more efficient then resistance heat. 

Ah, yeah, I have heard the "bad for your hair" part.  Didn't know the bit about vitamin D though, thanks for sharing.  I haven't been sick for 3 or 4 years now though, which is nice.  Guess I'm getting enough D then?    I own a convertible, and put the top down even in 30 degree weather though, so maybe I'm just a bit on the odd side...

I forgot to add "for your hair" as well, though guys usually don't care about that. My hair is 1/4" long, so I obviously don't care much about it. But most women do, so we guys should spread the word to them.

Soap and hot water every day is the fastest way to dry out your skin (and hair) in the winter. And our bodies produce Vitamin D by being in the sun -- but here's the catch: you have to wait 48 hours after being in the sun for most of it to be absorbed by the body. So daily showers wipe out the lion's share of it. Vitamin D does more things than I can count, including keeping your immune system in top condition (one of the reasons more people get sick in the winter -- most people don't go outside as much, plus there isn't as much sunlight, and people are more covered up)

I agree, one always feels clean & relaxed (and awake) after a shower -- but it's good to weigh the two and strike a balance.

I think it's only America that is fanatic about once-a-day showers -- most other countries have a long tradition (of common sense?) that doesn't dictate such.
(FYI, I'm an American living in America)

Really?  Didn't know that... I usually end up with a shower every other day, namely because I only wake up on time that often.    But I would prefer to take one every morning, just for the "wake-up" factor.

That's nice that you have natural gas for a backup and all, but you really don't need to shower every day in the winter, unless you're doing some *serious* physical work indoors...

It's actually not good for your skin, or your Vitamin D absorption.

Here in Kansas I use natural gas for heating, and my water heater.  I prefer this so that when power goes out during a winter storm, I can still light my fireplace and have hot water to shower with before I go to work (since my work has a generator, I still have to go to work even if we have a city-wide power outage)

Absolutely depends on where you live.

Completely untrue.  Again, it depends where you live.  In my hometown, I'd say the majority of people heat with electricity.  Heatpumps, if their house has been properly retrofitted, but I know one guy who heats with ceiling heat still, and ends up with a bill around $300 during the winter.

Point is, a lot more than just 1% of people use electricity for heating.  It just depends where you live, and how cold it gets during the winter.

Well, not everybody is living in the southern US.
Here in central Europe gas comes from russian pipelines and electrical power from monopolized hydropower. I think you'd be able to know what figures this leads to... 

Well good thing they don't charge a "magnitude more".

1 Therm of natural gas in the US averages $0.85 delivered.
1 Therm = 29.3 kwh

In southern US winter time rates are usually ~$0.08 per kWh.
$0.08 * 29.3 = $2.34 per therm.

A heat pump achieving only a COP of 2.4 is cheaper than 92% efficient natural gas furnace.  Heat pump is simply an AC unit in reverse so buying a high efficiency heat pump has the advantage of getting a high efficiency AC unit for summer time usage in the same unit.  In a place like TX where temps are high and summers long that makes a lot more sense than buying a high efficiency furnace and using natural gas and then needing to either waste electricity in summer or spend even more getting a high efficiency AC unit.

Heating oil?  Are you kidding me.   Heating oil is insanely expensive about $2.60 per therm.

A heatpump with a COP of <1 is cheaper.  However heatpump will never have COP of <1 because worst case scenario it will switch to resistance heating and be 100% efficient.

Well, those are all 'up to' numbers.  Yes in some cases you are probably better of with a heat pump, but as long as power companies charge over a magnitude more for electrical power as for gas or even oil it is still cheaper to use that.

Still, natural gas is much cheaper in practical use (enduser prices), transmisson losses are usally greater than 10% and heat pumps you can actually buy have less efficiency than 500%.
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Actually no.  In many parts of the US a heat pump IS cheaper than natural gas furnance.  The two conditions are a) cheap winter time electrical rates and b) winters which don't have many days below 10C.   Efficiency falls off a cliff below 10C and below 0C will often require resistance heating. 

Generally areas with very hot summers need a lot of electricity in summer thus they have huge amounts of available capacity in the winter driving down winter rates.  Those areas also tend to have milder winters.  That is perfect combination for heat pumps.

Also if you are stuck on natural gas they do make natural gas powered heat pumps.  Not that common though because until recently natural gas prices were much higher relative to electricity.  With low natural gas likely in the intermediate future natural gas heat pumps may become more common.  Get >100% efficiency AND the lower cost (per unit of energy) of natural gas.

Also BTW:

Average transmission losses in the US are ~7%.
http://www.eia.gov/tools/faqs/faq.cfm?id=105&t=3 

There are 500% efficient heatpumps on the market.
http://www.mitsubishi-aircon.co.uk/default.asp?url=http%3A//www.mitsubishi-aircon.co.uk/mitsubishi_electric.asp%3Fid%3D169931
Well technically this one is "only" 433% (COP of 4.33).

http://www.waterfurnace.com/products.aspx?prd=Envision
(COP of 5.0) 5 watts of heat for every 1 watt of electrical power

Still, natural gas is much cheaper in practical use (enduser prices), transmisson losses are usally greater than 10% and heat pumps you can actually buy have less efficiency than 500%.

For many parts of the country/world a high efficiency heat pump is far superior to burning natural gas and almost anything is superior to burning heating oil.

Given top heat pumps can achieve 500% efficiency even if you used natural gas in a turbine to make electricity (60% efficient) and then lost another 10% in transmission (0.55% combined).  It is 5*0.55 = 275% or 175% more efficient than a non-existant 100% efficient natural gas furnace.