Heat Pump - Heat Pumps

Calliban · 2024-04-30 05:23:25

Installation costs are a lot cheaper than other estimates I have heard in the past. But they won't include all of the changes that have to be made to a property in order for heat pumps to provide enough heat. Properties must be well insulated, because achieving a high COP is not compatable with high heating temperatures. The lower the temp difference between radiators and the room, the lower the heat transfer rates. In fact, the best COP would be achieved by heating water to room temperature. But the amount of radiating area needed would be huge. Underfloor heating might work. Embedding heating pipes in walls would turn the walls into radiant heaters. That would be a good option for new builds.

In areas where urban development is too dense for ground source, a pipe containing flowing sea water could provide the heat source. It doesn't have to be warm, though it always boosts COP if it is. We could dump nuclear waste heat into a city sized salt water main. Suppose we have a pipe 50cm (1.5') in diameter, with saltwater flowing through it at 3m/s. Its temperature is 10°C and we remove heat from it until temprrature drops to 5°C. How much heat could it provide? Ans = 12.37MW. That is enough for a large town. The COP will beat air source heat pumps by a large margin, because there is no need for a high dP fan in a ground source heat pump. During summer, we would run the salt water mains in reverse, taking summer heat from the tarmac of roads and carparks and using it to recharge subsurface heat reservoirs. This ensures that come winter, the salt main temperature can be kept at 10°C, regardless of the outside air temperature.

Last edited by Calliban (2024-04-30 05:34:55)

SpaceNut · 2024-04-30 17:43:15

I have an installer that works with me so I am hoping that I might get what I need from this gentleman even if its broken at least I can learn and build on the cheap.

What are heat pumps and could they help your home save energy?

The Significance of Heat Pumps in Promoting Sustainable Building Methods and Attaining Energy Efficiency Goals

https://en.wikipedia.org/wiki/Ground_source_heat_pump

Of course, size starts with a simple sq ft of the home to heat assuming the normal 8 ft ceilings.
Heating Specialists on Thumbtack cost $9000 - $50000

Horizontal loops are the most common and cheaper of the two standard ground loops because they only require a trench depth of 4-6 feet. This doesn't usually require any special digging equipment, which helps keep the cost of installation low. However, you need a lot of land to install a horizontal loop large enough to absorb and transfer heat into the ground, especially for larger buildings.
Horizontal ground loops typically require 400-600 feet of pipe (depending on the efficiency of the soil and the pipe material) for every ton of cooling and heating capacity. The average geothermal home system uses a 2-3 ton heat pump which means well over a thousand feet of pipe for even a small system.
Many horizontal loops are buried under spacious areas like parking lots or parks, but a large yard (enough to lay 1,500 - 1,800 feet of pipe for a 3 ton heat pump) can provide enough space for a horizontal loop with the right layout. Ask about layout options like coiled loops to save you space and keep you from installing the more costly option—vertical loops.

Calliban · 2024-05-01 05:02:18

For residences that don't have space for a ground source heat pump, maybe a tank of water could be used as the heat source? Lets say we start with water at 7°C and use a heat pump to suck heat out of it freezing it. For each litre of water frozen, the heat pump will extract 0.1kWh of heat. A cylindrical tank 3m in diameter and 3m tall, would provide some 2100kWh of heat through its phase change to ice. That is enough heat to meet the heating needs of a well insulated house for about 1 month. When temperatures outside rise above freezing, we would open vents and use a wind catcher to blow air through the ice store, gradually remelting it. During summer, we would use the wind catcher to collect warm air, preheating the tank ready for the beginning of heating season in the autumn.

Something like this would work in locations where temperatures only occasionally dip beneath freezing and only stay beneath freezing for a few weeks at a time. Most of Europe meets that description. Deep ground temperatures average about 10°C. Here is seasonal average temperatures for Edinburgh, which is colder than most of UK.
https://www.metoffice.gov.uk/research/c … /gcvwqum6h

The tank is effectively a thermal capacitor, drawing energy from the wind. If we take the average windspeed to be 6m/s, the specific heat of air to be 1KJ/kg.K, its density to be 1.22kg/m3 and assume we drop its temperature by 1°C. Assuming a 1m2 catchment area, how much energy flux can we get into the tank when outside temperatures are above freezing?

Q = 1 x 6 x 1.22 x 1000 = 7.32kW

This comfortably exceeds the heating loads of most residences. Drawing heat from a source at 273K and providing heat at 303K (30°C) woukd give a Carnot COP of about 9 in tge dead of winter. In autumn and spring, temperatures will be higher and COP will be better.

Last edited by Calliban (2024-05-01 05:14:38)

tahanson43206 · 2024-05-01 06:35:55

For Calliban re water tank thermal capacitor ....

Post #28

Thanks for providing this interesting alternative to use of soil as a heat source...

Zoning laws in much of the US would prohibit an above ground tank, but should have no problem with an under ground one.

An ideal location in much (if not most) of the urban US would be under the outside (detached) garage.

The garage design would need to be enhanced to support the concrete floor over the water tank, and a layer of insulation would help to keep the garage temperature independent of the water tank, which would fluctuate as heat is invested or drawn out.

It seems likely to me that zoning laws in Europe are similar to the US, since much of US sentiment derives from European precedent.

Is your water tank proposal more likely to win acceptance if it is located under a small garden (for example) than above ground?

Is is correct to think that the performance of a water tank as a thermal capacitor would be superior to ordinary soil used for the purpose? You have often spoken of the poor thermal conductivity of materials such as stone.

One detail is worth further study ... water will increase in volume as it freezes, so I assume a tank designed for a freeze/thaw cycle would be able to deal with the stresses?

(th)

Calliban · 2024-05-01 09:16:48

This article discusses the possibility of cold district heating for densely populated urban areas.
https://theconversation.com/no-space-fo … ing-180005

In this concept, every dwelling would have a heat pump. But the heat supplying the heat pumps would be drawn from a water pipe carrying cold water that supplies entire streets. These water mains would extract heat from boreholes, which would store summer heat for use in winter. The distribution pipes don't need to be anything special. Just a big concrete underground pipe that serves as a heat source for individual heat pumps.

One thing I did notice when reading about heat pumps, is that larger systems appear to achieve scale economies. The purchase cost of a heat pump providing twice as much heat will be <2x greater. It therefore makes sense providing heat pumps that serve multiple homes. That is the most capital efficient solution. But there does need to be an authority that does this on behalf of a town or it won't happen. It requires collective action. Probably the best solution would be to run the cold water pipe down main streets. Heat pumps would be located at street intersections and would provide heat to entire branching streets.

Last edited by Calliban (2024-05-01 09:24:10)

Terraformer · 2024-05-01 09:44:20

Anchor customers should help with the economics here. If there's a hotel nearby, there's a customer who has a high demand for hot water, making it a far easier sell than having to sign up most of the street. So long as the system is sized right it can be expanded as needed to supply more people.

tahanson43206 · 2024-05-01 10:51:51

For Calliban re #30

Thanks for finding and posting this link ...

I've made a note to come back later to read the article.

A question I'll have is whether the water flowing is fresh potable water or sea water or perhaps river or lake water. The cost of potable water in these quantities would be far greater than least cost water. The depleted energy water needs to go somewhere to be recharged with thermal energy, so I'll be looking for how that is handled, as well.

(th)

Calliban · 2024-05-01 11:09:28

Salt water is less likely to freeze, so would be functionally better. But corrosion would be more of a problem. I don't think the cost of water will be at all problematic if the heat network works on a circuit. A typical dwelling in the UK needs about 10,000kWh of thermal energy each year. At peak winter times, heat demand would be something like 3kW. That is 0.14 litres per house per second, assuming a 5°C temperature drop across the heat exchangers. Assuming that water is cycled once per hour across a town network, that is a water inventory requirement of 514 litres per dwelling. That would be a burden if water isn't recycled. But it isn't a problem if water is reused.

tahanson43206 · 2024-05-01 11:30:13

For Calliban re #33

So the existing fresh water supply could be enlisted for this purpose?

The existing supply is drawn down by customers who use the water for a variety of purposes, and then exhaust the spent water to the recovery systems. Very few of these are closed cycle (to the best of my knowledge). Instead, the treated effluent is exhausted to the nearby river, so it has time to mix with river water before it enters the next town's intake down stream.

On Mars, a closed cycle is needed.

On Earth, a closed cycle would benefit everyone, but humans have avoided the cost of treating their waste by dumping it on the neighbors for millennia.

In today's more enlightened cultural milieu, it is possible citizens might be willing to pony up to pay for total recycling of water.

That could include adding thermal energy to the supply at the reconditioning and purification facility. The water exhausted to the effluent path would be loaded with contaminants and drained of thermal energy.

Such a system might work well on Mars to distribute fresh water and thermal energy within a habitat cluster.

(th)

tahanson43206 · 2024-05-01 11:40:37

For Calliban re #33

In thinking about your proposal further, I realized that the (good sized) community near me uses natural gas to provide heating service. Your proposal would allow construction of a large community that does not depend upon natural gas. It ** would ** depend upon a reliable supply of electricity, and a reliable supply of potable water for normal uses ** and ** for heating in winter and for cooling in summer.

This suggests that water flows out of the home or business need to be kept separate.

The water consumed for normal purposes must enter the flow for recycling.

The water consumed for heating or cooling needs to return to a separate facility for heating or cooling.

Thus, this scenario would replace the existing three pipes system with three pipes.

Now we have:
Pipe for fresh water
Pipe for natural gas
Pipe for water exhausted from the home and loaded with contaminants

Future would be:
Pipe for fresh heated water (or cooled water in summer)
Return pipe for thermal water
Return pipe for normal contaminated water.

Electricity consumption would increase, but natural gas energy consumption would drop to zero.

Note a detail: At present, fresh water arrives at the home at the temperature of the soil around the pipe from the street.

In the new scenario, fresh water would be elevated in temperature so it would arrive at a higher temperature, and would thus have to be cooled for drinking.

(th)

SpaceNut · 2024-05-01 17:37:19

Sizing of a heat pump BTU and tons to wattage used to produce the heat required.
Heat pump sizing guide: Bigger is not better

Size is also known as capacity, measured in tons or Btu. One ton equals 12,000 Btu. The goal is to match that size with your home's needs on the coldest and/or hottest days.
Simple sizing rules are basically worthless
The first page of Google is filled with terrible advice about heat pump sizing. You'll find a wide range of shortcuts and rules of thumb that can't all be correct, including:
Multiply the number of square feet of living space in your house by 30
Multiply the square footage by 20
Add 1,000 Btu for every 100 square feet—in other words, multiply the square footage by 10
Multiply the square footage by somewhere between 30 to 60, depending on your local climate
Start with 1 ton for the first 1,000 square feet, and then add an extra ton for every additional 500 square feet
So for a 2,000 square-foot house, you're left with estimates from as low as 20,000 Btu (theoretically possible for milder climates or very well-built homes, but unlikely) up to 120,000 Btu (certainly wrong). And each of the estimates in between could be off by at least a half-ton.

How Much Power Does a Heat Pump use? (1-5 Tons)

Heat pumps use between 545W and 4,286W of power depending on unit size and energy efficiency. An average heat pump runs on 667W of power per ton, with a seasonal energy efficiency rating (SEER) of 18. A 3-ton unit, therefore, needs 2,000W of power and costs you $1,533 a year.
Formula:
Unit size (in BTU/h) = Unit size (in tons) × 12,000 BTU/h
Total Wattage (in Watts) = Unit size (in BTU/h) ÷ SEER (in BTU/Wh)

So, if I used my winter electric - summers bill. I know the heat portion of the requirement to stay warm with my current methods.
Its roughly 50 kwhrs a day of power being used.

If I, then can calculate a source to provide this then I have achieved a desire cost but that's provided that I can do such a feat.

tahanson43206 · 2024-05-01 18:04:15

For SpaceNut re #36 and discussion of heat pump sizing....

An HVAC system does not run all the time...

If the home reaches the settings on the thermostat, the system wouid normally shift into low fan mode to just keep air circulating in the house.

Even in the depths of winter, I have observed that the furnace reaches the target I've set and goes into low fan mode overnight. Now that summer AC season has arrived, I see a similar pattern.

I would imagine a heat pump would operate in the same manner, but presumably more efficiently, since it would be cycling fluid instead of air.

Do any of your calculation systems (as shown in the post or otherwise) take that into account?

(th)

SpaceNut · 2024-05-01 19:04:26

Well, running has to do more with not just how cold or hot the temperatures are outside but also on how drafty the place is so you always need more than what the rules of thumbs indicate. I have no exact figure until I make use of one.

How Much Electricity Does Heat Pump Use? (+ Running Cost Per Hour, Day, Month)

The heat pumps are more efficient so if I am spending more than the above wattage its not benefiting to install one.

here is the air to air system

Here is the electrical to heat Heater Room Size Calculator: What Size Room a Heater Heat?

Seems that a 1,500 BTU Heater Room Size: 50 sq. ft. or 1,500 Watt Heater Room Size: 150 sq. ft. by changing the units in the calculator.

so, at 40kwhr /24 hrs = 1 2/3 kw for 800 sq ft. with a heat pump 30,000 to 36,000 BTU = 3 ton heat pump to heat my home.

SpaceNut · 2024-05-02 10:14:28

How Heat Pumps Could Save Most Americans Money on Energy

This is a split type of air-to-air design.
BB1il459.img?w=768&h=495&m=6

https://www.nrel.gov/news/press/2024/be … eport.html

Nationally, heat pumps would reduce home energy use by 31% to 47% on average and residential greenhouse gas emissions by 36% to 64%, the study found.

SpaceNut · 2024-05-03 07:48:08

Study answers common question about impact of heat pumps: 'It's better to switch now rather than later'

Installing heat pumps is a win-win for both households and the planet.
Eric Wilson, a senior researcher at NREL, told Canary Media, "If every American home with gas, oil, or inefficient electric-resistance heating were to swap it right now for heat-pump heating, the emissions of the entire U.S. economy would shrink by 5% to 9%."
For those interested in making the switch, Rewiring America offers a free service that provides an estimate based on your home's needs. There are also rebates available through the Inflation Reduction Act and tools to help you make the most of them. If you don't want to completely change your current heating setup, micro-heat pumps are an affordable supplement.
The bottom line is that the average household can make a significant impact, even when drawing from a dirty power grid.
"It's better to switch now rather than later," Wilson said, "and [avoid locking yourself into] another 20 years of a gas furnace or boiler."

Well inflation makes the items more expensive in the future but the lost amount of atmospheric change is the bigger gain by switching to a green energy source.

Calliban · 2024-05-09 03:37:57

Two years of living with a heat pump.
https://m.youtube.com/watch?v=94jy8aLqLms

This looks like an air source heat pump to me, though the owner does not say as much. His COP is about 3.5. Given the difference in price between electricity and gas, his heating costs end up being about the same. He lives in the north east of England i.e. Geordieland. Which is colder than most of the country. He also appears to live in a terrace house, which would make ground source difficult if not impossible.

For the most people in the UK, there simply isn't enough outside space for ground source heat pipes. But water pipes could be used to supply heat at a constant 12°C throughout the cold months. This would substantially increase the effective COP of heat pumps in winter.

A few weeks ago we discussed a district heating system that was capable of heating a small town. A cold heat network would represent the lowest upfront capital cost, as it really doesn't require any complex engineering. Just a concrete pipe carrying sea water circulating through a soil body. Heat transfer coils for individual houses could be wrapped around the pipe. The good thing about this concept is that it can begin on a small scale. Individual streets can have their own water mains drawing heat from whatever source happens to be nearby. This could be a nearby field with boreholes drilled into it. Or a stream. Or maybe a nearby hill that can be used as a thermal store. The water in the pipe does not need to be particularly warm. During the summer, the loop would operate in reverse. The street will act as a solar collector, gathering heat at 15-20°C, which can be returned to the soil or rock body used as a thermal store.

Last edited by Calliban (2024-05-09 03:49:10)

tahanson43206 · 2024-05-09 08:37:17

For Calliban re #41

Your statement about ground source heat pumps, and the surface area required, would certainly make sense if a traditional field of pipes laid just below the surface is what you have in mind.

However, a vertical heat store should be possible for a much smaller permanent area.

If you have time, and if the subject is of interest, please compare the costs of a field of coils vs that of a vertical store of equivalent capacity.

I bring this up because it appears (from hints we've seen from Internet reports in recent times) that advances in vertical drilling technology are happening.

If the cost of drilling a vertical shaft is reduced, then a vertical heat store may become more attractive.

In the process of doing that evaluation, please compare the efficacy of use of water as the heat storage medium instead of moist soil.

I would imagine water might be a better overall heat storage medium.

A vertical store would need walls to maintain the shape of the store over time.

Metal is a candidate material, but ceramic or concrete might be attractive as an alternative.

The shaft need not be water tight, unless there is a risk of loss of water to the surrounding underground material.

The water table varies from one location to the next, and it also changes over time, so the question of whether to seal the store or not might not have a simple answer.

Never-the-less, if you were to advise a home owner about how to implement thermal storage and heat pumps most effectively, perhaps a vertical store might make sense in some situations.

(th)

SpaceNut · 2024-05-09 17:39:19

vertical well vertical borehole system, only a width of 100-150 mm of garden or driveway space is required per borehole. The depth of each borehole typically ranges from 60 to 230 mm

same as an artesian pr drilled well.

tahanson43206 · 2024-05-09 18:04:12

For SpaceNu re #43 ...

Thanks for finding and showing the article about vertical and horizontal thermal energy storage and retrieval systems.

The abbreviation "mm" may stand for meters? The abbreviation is not clarified.

For me, "mm" means millimeter, so the article was a bit confusing.

(th)

SpaceNut · 2024-05-09 18:25:24

Ya it could be clearer
https://www.greenbuildingadvisor.com/ar … s-of-thumb

tahanson43206 · 2024-05-10 08:33:01

For SpaceNut ...

This YouTube may be of interest: https://www.youtube.com/watch?v=MUWjjjFgXdg

However, I paused the video and just read the comments.

The video garnered a lot of comments, and most were quite interesting.

One comment reminded readers to avoid pure water as a fluid, because it dissolves metal.

Most folks seemed to be using glycol mixed with water.

The video itself seemed to have won viewer approval.

(th)

SpaceNut · 2024-05-10 16:44:14

Due to temperatures approaching freezing and boiling under the extremes of a given region.
It requires food grade if it's going to heat drinking water.

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#26 2024-04-30 05:23:25

Re: Heat Pump - Heat Pumps

#27 2024-04-30 17:43:15

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#29 2024-05-01 06:35:55

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#30 2024-05-01 09:16:48

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#31 2024-05-01 09:44:20

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#32 2024-05-01 10:51:51

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#33 2024-05-01 11:09:28

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#34 2024-05-01 11:30:13

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#35 2024-05-01 11:40:37

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#36 2024-05-01 17:37:19

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#37 2024-05-01 18:04:15

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#38 2024-05-01 19:04:26

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#39 2024-05-02 10:14:28

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#40 2024-05-03 07:48:08

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#41 2024-05-09 03:37:57

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#42 2024-05-09 08:37:17

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#43 2024-05-09 17:39:19

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#45 2024-05-09 18:25:24

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