Steam from Heat Pump

Since residential steam is increasingly becoming a niche market I doubt the money is there to develop these systems for people like us… but that would sure be nice!

Are you guys talking about compressing steam?

They talk in the article about compressing the refrigerant to a higher pressure but don't say a word about how this is done. Either a compressor or another heat source would be needed.

Going from a -15 F source to 220 F sink to make the steam is a pretty big ask, if the COP is kept up (as I noted, it must be greater than 3 under those conditions to be viable). There may be such air to water heat pumps out there. Kindly publish the maker and models, as I've never seen one, and to be a bit brutal about it, I have grave doubts.

Suggesting going to an assisted vacuum system (which would be required) to lower the steam temperature is fine, but remember three things: you've just made an exceedingly simple heating system into one which is remarkably complex; second, it is a truly remarkable steam heating system which is vacuum tight; third, you lose radiation power at a near linear rate with reduced temperature, and you may not have adequate radiation.

I will repeat a challenge which I made some years ago, which no one took me up on: it is simply this. I will provide an existing two pipe vapour steam system in very good condition, in an existing structure, with energy use records going back 20 years. You will provide your heat pump system, which is required to have a COP of not less than 3.0 at a source air temperature of -15 Fahrenheit and a net output of not less than 400,000 BTUh at 15.0 psi absolute steam pressure. The system must have a failure rate of less than one failure to operate requiring maintenance per year. If the system requires more than 8 KW of power to operate, the cost shall include a suitable, fully automatic, power source capable of maintaining not less than 7 days of continuous operation without grid (commercial) power. If under any operating condition the system requires more than 24 KW of power, the cost shall include all necessary additions and modifications to the service entrance an electrical equipment. If, after 15 years of running the system, including all energy costs (note: I have a PV system, but energy costs shall be figured at retail public utility rates), initial capital investment depreciation, the cost of loss capital opportunity, and all maintenance, has cost less than replacing the existing oil boiler would have, I'll buy it from you for cost plus a reasonable profit plus market rate interest. .

No subsidies shall be included.

Edit: two more things. First, If the system as installed fails to operate as required above at any time in any respect, you will bear the entire costing of removing the system in its entirely, except for electrical modifications which may have been required, and restoring the existing steam system to its present condition or better. Second, a "failure" is defined as not more than 24 hours out of full operation for any cause requiring maintenance. Each succeeding 24 hours shall be regarded as a further failure, and so on.

That's your competition.

Time to put up or fold, folks.

I have no need for air conditioning.

I am asking for an essentially drop in replacement for Cedric. Somewhat tongue in cheek, because I know you can't do it, any more than a Tesla can self drive itself from the nearby village to Cedric's home (2.5 miles).

I love unicorns and rainbows as much as the next guy or gal, but I live in the real world — and so does the vast majority of the population.

The average American lives in a city or a suburb somewhere where the design temperature is above 0. The average Brit lives similarly. I'm fine with them having heat pumps. No problem. In fact, I would recommend them for new construction. Just stop pushing heat pumps as a solution to staying warm in climates and situations where they just don't work. For reference, the Brits and Germans tried that — and it brought down the governments.

Heat pumps are of course very competitive in rural areas too, often more so because you’re competing against higher cost fuels.

@WMno57 I truly do not care how much a replacement battery for a 16 year old Camry costs. If you don’t want a Camry hybrid, don’t buy one.

That’s yours?! Beautiful!

I believe that stat is 90% of US homes have AC (including non-ducted). Need isn’t the same thing as want - Americans want AC, and they want it enough to pay for it.

If I had to use air source electric heat pumps to replace steam heating boiler I'd consider compounding. For example regular heat pump to heat condensate to 120° and compress that to steam.

Since this thread was from April, I wonder if it started on April 1?

As I said, if you know their limits, heat pumps are great. If you try to use them beyond their limits, they are horrible.

My house was built in 1935. It has blown in insulation and more modern windows, but it can't compete with a modern tight house.

It has a single pipe steam system with the original radiators, which probably means too much radiator area for its current heat load.

What happens in middle of winter is that the oil system does a great job of keeping my house comfortable. But in the fall and spring (when I only need a little bit of heat), I hear the boiler kick on, spend 10 or 15 minutes making steam; then the steam makes it to the radiators, and a couple of minutes later there is enough heat in the living space that the system shuts off. When it is cool but not cold outside my oil system is horribly inefficient.

Heat pumps, on the other hand, are more efficient the warmer it is outside.

The two systems complement each other perfectly.

When the temperature is above freezing, I run minisplit heat pumps. When I only want to heat one room, I run a single heat pump. When I want to heat my whole house and it is below freezing, I use the steam system.

I checked my year over year bills. Over the entire year, I needed 1000 additional kWh, and used 200 gallons less oil. This is a huge win. But my guess is that to completely transition I would need 3000-4000kWh to cover for the next 130 gallons of oil. 5000kWh to avoid using 330 gallons of oil is not much of a win. One very nice benefit: my oil use went down enough that I only need my tank filled 1x per year, in the summer.

-Jonathan

I'm pretty comfortable with my math.

I recognized that the COP value implied by my savings is unrealistically high, which is why I said that to eliminate the next 130 gallons of oil I would need far more electricity. As I said, over the entire year I used 1000 kWh more electricity and 200 gallons less oil, but to eliminate the final 130 gallons of oil use I'd expect 3000-4000 kWh more.

I replaced an old central ducted air conditioning system with minisplits. The minisplits were more efficient as air conditioners than the old AC, so my summer electricity use went down. That is part of my savings, but I think it is fair to include it since installing the minisplits was the cause of the improvement.

I use the minisplits for heating only when the outdoor air temperature is above 32F, or above 20F if I am only heating a single room. When the outside air temperature is above 32F, the minisplits are more efficient than when it is colder, and when I am only heating a single room the heat load of the structure is lower.

My steam system has an 85% efficient boiler, but I expect that in the shoulder seasons when the house doesn't need much heat the practical average efficiency is much lower. Perhaps you can help me understand the practical efficiency of a boiler including the heat required to bring a cold boiler up to steam temperature before heat is actually being delivered to the habitable spaces of the house. I am using 'practical efficiency' to describe the BTU delivered into the living space divided by the BTU of the oil burned. It doesn't matter if the peak efficiency of the boiler is 85% if, because of how the boiler is being used, most of the heat doesn't actually make it into the living space.

Naively, if the boiler runs for 10 minutes, but steam is only being distributed for 1 minute, I'd expect the efficiency to be below 10%. But the boiler is in the basement, so any heat leaking out of the boiler is heating the basement and then the rest of the house. On the other hand, any heat going up the flue is wasted or worse, because the air going up the flue has to be supplied somehow.

Arguably my boiler is oversized; on the coldest day I've experienced the boiler ran for about 6 total hours. This probably lowers the practical efficiency because there is more boiler mass to heat up in the first place.

In any case, I suspect that the practical efficiency of my steam system is well below 50% when very little heat is required by the house, so by getting rid of that particularly inefficient use I see a huge reduction in annual oil consumption.

I agree that I've made my system more complex. Not sure how much of that complexity can be buried so that it doesn't really bother the user.

One can save energy in special circumstances. For example waste heat from refrigeration can be boosted –in effect heat pumped– to useful temperatures. Frigid air is not an ideal source. Geosources, especially unlimited water supply, is more amenable. I believe WW II German submarines used heat pump for heating. Chemical industries like oil refining often have waste heat that can be mechanically pumped to higher temperatures like steam. Rich people with waterfront properties often use heat pumps.

Frigid air is not an ideal input heat source, but once you consider the installation costs and loop pumping costs of geothermal sources, air source heat pumps compare surprisingly well.

-Jonathan