10 mega-watt hours

You might also try looking at the wind at different altitudes. Above about 8,000 meters, you'll start to see the jet stream. It's really obvious at 13,500 meters (highest altitude available).

Also, if you click on the arrow in the lower left corner, the display will fast forward into wind forecasts for the next 5 to 8 days. It's kinda interesting to see the changing wind patterns with time, especially if there's a storm nearby or passing through.

If you zoom in to your area, the display will show various weather stations. These tend to be the better weather stations from the University of Utah MESONET network. It offers local wind history graphs and forecasts.

Have fun...

WOW! They ALLOW you to give the utility energy for free! What an incredibly generous deal!

Jon

We just replaced our entire HVAC-oil-furnace stack, and elected the heat-pump option instead of a simple AC compressor. I've been taking some performance measurements, e.g. with Tout = 45 deg, it takes the heatpump about 1 hour to raise the house temp by 2 degrees. It consumes 5kW, so that's 2.5kWh/deg. Whoa, we'll be using far more electricity than our roof makes! The default outside-temp breakpoint for switching to the oil burner is 40 degrees. I'm studying the thermostat manual's installation instructions to change to 50 degrees. They claim heatpump heating is cheaper than oil, but I doubt it! Anybody have experience with a hybrid system?

Time marches on and at some stage Tompson won't be able to actuate a keyboard with his flabby fingers. Does his daughter know what he has actually typed on this forum? He is equally as bad as the worst Muslim misogynist.

Heat-pump heating is cheaper than oil per kilowatt-hour delivered if the te mperature difference between the inside of the house and the external radia tor is small enough.

The real advantage obviously is that the heat pump can go both ways - to co ol the house in summer and to heat the house in winter.

In Sydney it's a good deal. In the UK you needed a bigger heat pump to supp ly the heat you needed in the depths of winter, and the capital cost got a bit out of hand. I never did the sums myself, but I knew people who did.

If you could super-insulate your house to start with, the heat pump made mo re sense - the 150 Watt you generate all the time (alright 100 Watt when re sting, about 150 Watt when doing stuff and anything up to 600 Watt when doi ng hard physical labour) started being a significant part of the heat you n eeded in the depths of winter.

Using a buried heat-exchanger coil also made sense - about 50cm of dirt is about six months of thermal lag, so some of the heat you pumped into the gr ound in summer could still be hanging around in winter when you needed to p ump it back out - but it's even more capital investment.

That depends very much on the specifics of the heat pump (COP) and the price of the two fuels, and the efficiency of the oil burner. In many cases it's true, particularly with a proper cold-climate heat pump (which a 40 F switchover - does not sound like.)

The good cold-climate mini-splits will put out 3X the heat (COP of 3 or more) as the electricity put into them, and operate effectively down to sub-zero F temperatures. For whatever reason most whole house systems are still sucky southern-oriented things with lousy COP and poor cold performance.

It's been an included line on the Vermont Fuel Price Report for a couple of years now with some assumptions you can read about and prices that may vary from your own local prices. The VFPR is one of the clearer expositions of these trade-offs on the net - If Mass. makes anything like it they hide it well, but I bet they simply don't.

But it's green >:-} ...Jim Thompson

Gotta be a patriot and burn somma that Montana crude.

Whoa, 3x! Is that at high outside temps? Apparently my system will work fine to far below freezing (runs at 40-degrees with a modest duty cycle), even includes automatic defrost features. Maybe the default 40-degree setting is considered an economic tradeoff point. Our installer says the electric heat-pump is cheaper down to 40 degrees; clearly I need to research the numbers.

It varies with the specific unit and the specific temperature. If you look at the October, 2015 VFPR they discuss it vaguely and have a vague diagram with an unlabeled temperature axis to go with their guesstimate of 2.4 (240%) for Vermont conditions (which of, course, are rather variable from one end of the state to the other, plus they are trying to get an average seasonal number.) Your conditions in Eastern MA may be somewhat more favorable. COPs around 3.5 at moderate (40's F) temperatures are not uncommon.

At current Vermont prices and the 2.4 COP guesstimate, oil has a slight edge per the September, 2016 report. Having see twice the price on oil and pretty much the same price on electricity in the past few years, that is not a static situation, and it's also not static with outside temperature since the COP varies with that.

Ideally, you find a specific diagram (or table) that's specifically labelled for your particular unit, and then you can plug in price of electricity, price of oil (cost of what you have in the tank or replacement cost, as you prefer) and temperature to see which is cheaper, when. When oil is cheap and electricity isn't, that will be different than when oil is expensive and electricity still is kinda expensive. If you expect the election-year low-price-oil to last, history may have an opposing view.

If you really want to be an efficient whacko, get a diesel generator and put your heating oil through that, recover the high quality waste heat directly, use the electricity generated to run your heat pump, and put the otherwise unrecoverable waste heat into the path of the heat pump's outside unit ;-) But then you'll have to pay sales tax on your heating oil...and it's a good deal of capital expense.

Having just done the replacement, your only economically sensible option is to try and get the data on what you got, and then figure out where the tradeoff temperature is as prices shift.

They claim

Yes, I have a hybrid oil heat pump system. My COP is about 3 and that makes oil at $2.00 per gallon equivalent to about $0.18 per kWh of electricity. So it depends on what YOU pay for each fuel.

And then there are those pesky intangible issues. What is the wear and tear cost on an AC compressor vs an oil burner?

How comfortable is your house when the vent is blowing 80 deg air from the heat pump vs 120 deg air from the the oil burner?

And the heat pump compressor includes a crankcase heater that runs 100 Watts 24/7 to keep it warm so it can start anytime. Freon will migrate to the coldest part of a system when it is off and you don't want your compressor full of liquid Freon when it starts, so they keep a heater running in it 24/7.

And below about 32 the outside coils can freeze up and the system has to run in reverse defrost mode for a few minutes.

My bottom line is, once the temp is consistently below about 35, I turn off the heat pump, switch off its breaker to kill the heater, and keep it from coming on, and I stick with the oil. I just hope oil stays around $2 per gallon.

In spring I turn the breaker back on a few days before I let it run so it warms enough to drive the liquid Freon out before I let it start.

mark

On Wednesday, October 12, 2016 at 10:33:10 AM UTC-4, snipped-for-privacy@ieee.org wrot e:

s about six months of thermal lag, so some of the heat you pumped into the ground in summer could still be hanging around in winter when you needed to pump it back out - but it's even more capital investment.

All of the data I have seen on soil temperatures does not agree with your s tatement of 50 cm giving a six months thermal lag.

Dan

ote:

is about six months of thermal lag, so some of the heat you pumped into th e ground in summer could still be hanging around in winter when you needed to pump it back out - but it's even more capital investment.

statement of 50 cm giving a six months thermal lag.

So post some of it. My figure is dredged out of memory. If you've got a bet ter reference it wouldn't have to be all that good to be pretty convincing.

The more general point - that a buried heat-exchanger is a good idea - stil l stands. It's economic viability usually does seem to depend on somebody w anting to do a lot of earth-moving anyway.

Right, it's entirely a matter of the available water. Maybe a small well, tapping an underground aquifer. Slightly complicated if you don't have a well.

It isn't. You just bury a long enough loop pf closed pipe and circulate your water - other heat exchange fluid - through it. You need to be in contact with a much larger thermal mass than the heat capacity of your house.

Exactly, and for the time period in question. Here the ground can freeze down nearly a foot in winter. We get a situation where the ground below that is devoid of much water. That's a problem that has cost us several valuable trees, because we didn't water them midwinter!

I could solve that problem by running the pipe 100 feet down to a stream that runs through our back yard, and burying it deep there. Maybe get a 45-degree return fluid temperature in winter. The pipe would have to be insulated and buried the whole way, difficult with our yard's granite rock fill. A geothermal heat sink would be good for more efficient AC in summer. Might need our town's Conservation Commission permission. I've been thinking about it. Guy who installed our system has a geothermal hot-water heater, using an existing well on his lot. Research geothermal heat pumps. Probably just too many issues to overcome.

My Carrier 25HCC5 heatpump's COP is 3.88 with 47 deg (+8C) air, dropping to 2.64 with cold 17-deg (-8C) air. For 40 to 50-deg settings, and our $0.20 elec, isn't that close to a wash?

Whoa! 100 watts 24-7 = $175/yr. (Sadly I have 2 to 3 times that already in wallworts, etc.)

Yes, we have that aspect.

I looked at a bunch of sites before I started insulating the basement walls. But have not kept any links to the data. So if you are interested you can find the information as easily as I can.

A buried heat exchanger is a good idea. But when they are used for heat pumps they generally either use a couple of wells or trenches at least 4 feet ( 1.2 meters ) deep.

How large is your array - Watts? Sorry if you already mentioned.