Photovoltaics and Electric Steam Boiler for refurbished home

FuriousGeorge

The price per therm of NG is 0.33 USD. A KWh of juice is 0.15.

Assuming 75% efficiency for NG boiler systems and 100% for electric, I still get electric heat as 10x more expensive, or about 3.23 USD/therm equivalent.

I'm converting a 2-fam to 3, and for a variety of logistical and cost reasons, it makes sense for the entire building's energy bill to be paid by the owner. Each unit is about 1400 ft² (~130 m²). One of those is partially (50% or so) below ground.

I calculated that there is enough roof space on the home and garage to cover the yearly usage. In this state, the utility will repay overproduction, but you cannot produce more than you consume. I find their wording on the matter somewhat ambiguous, but I take that to mean you can have a production/usage ratio of 2. Otherwise, if it were 1, why would there be talk of credits at the end of the year? These credits can also be used to pay off the system.

I don't have enough space, in any configuration that I can think of to reach that level of production. Even if I could, however, I've never heard of anyone using PVs for domestic heat, around here (albeit indirectly). In addition, I'm sure I'm not the first one who's thought of this. My gut tells me it is probably a bad idea for those reasons, among others.

For instance, I don't know how much maintenance PVs require, but if they are offline for a good portion of the winter for whatever reason, now the home owner has a bill that is literally an order of magnitude higher than had they used NG, screwing up ROI.

I suppose this can be mitigated by a duel electric/gas boiler, but I'm unsure what other complications that might bring.

More worrisome are the unknown unknowns.

I'd appreciate any thoughts on the matter, or perhaps a more elegant solution.

For instance, I don't see any electric heating element designed to be added to the tank of a gas boiler system. To me, this seems like a relatively simple bit of engineering, but what do I know from boilers? There's probably a reason for that, too.

Larry Weingarten

Hello, Are you married to steam or could you use hot/warm water for space heating? If you could use water, then solar thermal could come into play. While PV is about 20% efficient, solar thermal is closer to 80%, so if you can use it, that would be good. Or you could look at a combined PV and thermal system like SunDrum. It seems a combination of solar thermal, heat pump and PV could do what you want, depending on how cold it gets where you are.

Yours, Larry

Jamie Hall

There are two major problems with using photovoltaics to provide electric space heating.

The first is getting enough electricity from them -- in any sort of reasonable space.

Let's suppose we have the latest gee-whiz (and very costly) photovoltaics, with a conversion efficiency of 20%. That means that when they are in the full sun, they will crank out 200 watts per square meter, which translates, very roughly, to around 60 BTUh per square foot. That looks encouraging, doesn't it? With, again, a very rough figure of around 20 BTUh per square foot for a well-insulated structure, you have excess power! Whee!

Look again. See that comment about "in full sun"? There are actually two parts to that.

The first, the more obvious, is that the sun has to be shining. It doesn't always. Together with that, that is the area measured perpendicular to the direction to the sun -- not the gross area of the panel. That means that to get that figure for more than a few minutes on two specific days of the year, you have to have sun tracking panels. Which do exist, but they aren't cheap. Let's get extravagant, though, and say we do have tracking panels. Now if you live in an area such as the desert southwest or southern California, where the sun really does shine most of the time, in the winter time you get 10 hours of solar input to your panels per day -- about 40% of the day. That doesn't matter in southern California -- you don't need the heat. It is a consideration pretty much anywhere else. So even in such areas your net gain drops to around 8 BTUh. In most of the rest of the country, a commonly used prudent figure is that you will have usable power output for around 12% of the time.

So our net power available in most of the country is around 2.5 BTUh per square foot of panel. To power even a pretty tight house then you require a total, tracking, solar panel area of perhaps 8 to 10 times the floor area of the house...

But this is a two pack game, and there's another joker.

You get no output from the panels when the sun isn't shining -- but the building will still need heat. That means that you are going to have to store that power you get from your panels (or pay the grid the big bucks to access their coal or NG fired plants...). If we get really optimistic and assume that the sun shines every day, if not all the time, then we need to store enough power to get through the remaining 20 plus hours of the day. A much more reasonable assumption is that you need to store power for three days at least. Again, for illustration, suppose that the building has a 100,000 BTUh heat loss at near design conditions. That means that in 24 hours, you need about 2.4 million BTU, which -- again very roughly -- works out to around 800 kilowatts even for one day, never mind three (it also works out to around 17 gallons of oil per day...). That, if your are still with me, means that you have some really big batteries -- and the ability to charge and discharge them at a high rate.

Good luck.

I might add, though, that with careful design and construction, it is possible to build a passive solar heated house (direct solar, not photovoltaic or pumped water) even in northern New England which works. I've done it.

FuriousGeorge

Larry Weingarten said:

Hello, Are you married to steam or could you use hot/warm water for space heating? If you could use water, then solar thermal could come into play. While PV is about 20% efficient, solar thermal is closer to 80%, so if you can use it, that would be good. Or you could look at a combined PV and thermal system like SunDrum. It seems a combination of solar thermal, heat pump and PV could do what you want, depending on how cold it gets where you are.

Yours, Larry

Thanks Larry. I'm going to look into this. I'm not married to steam. I've done a bit of research into switching to forced hot water already, but the current steam radiators are recessed into the wall. Replacing them with hot water radiators won't get me enough surface area to dissipate the heat I'll need (I think). Also, if I need to add a pipe, I'm not sure how much damage I'll have to do.

While this is a rehab, it's more about bringing it into compliance for a 3rd family. The interior is in excellent condition, and any damage I have to do will come out of the ROI pretty quick.

I think I need to more generally research solar thermal.

Larry Weingarten

Hi, I live in an off-grid home I built. I got to play with solar thermal for both DHW and space heat. I wound up building a gravity space heating system that puts finned copper tube (like is used for solar collectors) in the walls. It can keep the house at 70 with 80 degree water. So, if you go thermal, oversize the radiation so you can use lower temp water. Perhaps adding panel rads could help? Do have a look at SunDrum. One thing they can do is combine heat pump with solar thermal collectors, so you can collect heat at night, which is often when you need it... This means you don't need so much energy storage which @Jamie Hall pointed out so clearly would be just a bit of a problem

Yours, Larry

FuriousGeorge

Jamie,

Thanks for the well explained post. I keep accidentally deleting my reply. Let me try again:

Jamie Hall said:

That means that in 24 hours, you need about 2.4 million BTU, which -- again very roughly -- works out to around 800 kilowatts even for one day, never mind three (it also works out to around 17 gallons of oil per day...). That, if your are still with me, means that you have some really big batteries -- and the ability to charge and discharge them at a high rate.

That's similar to the number I came up with, but I may have come about it the wrong way. I took the 4.5 solar-hours/day the region gets, and figured I'd need a 50kw system to break even on yearly production. Not that I'm inclined to do it, but you don't have to store the power locally. You can instead deduct it from your bill, and at the end of the year you'll get a credit for any over-production, at a reduced rate. You'd produce 225 KWh/day which works out to 810,000 KW/day.

I said that I would have enough roof space to achieve that, but it looks like I miscalculated, and would actually only have enough for about 2/3 to 3/4, best case. I'd have to supplement anyway.

Jamie Hall said:

I might add, though, that with careful design and construction, it is possible to build a passive solar heated house (direct solar, not photovoltaic or pumped water) even in northern New England which works. I've done it.

I need to look more into this. My case is a retrofit, which will probably limit what I can do.

FuriousGeorge

Larry Weingarten said:

Hi, I live in an off-grid home I built. I got to play with solar thermal for both DHW and space heat. I wound up building a gravity space heating system that puts finned copper tube (like is used for solar collectors) in the walls. It can keep the house at 70 with 80 degree water. So, if you go thermal, oversize the radiation so you can use lower temp water. Perhaps adding panel rads could help? Do have a look at SunDrum. One thing they can do is combine heat pump with solar thermal collectors, so you can collect heat at night, which is often when you need it... This means you don't need so much energy storage which @Jamie Hall pointed out so clearly would be just a bit of a problem

Yours, Larry

Thanks for the pointers. I'm going to look into all of it. The house is brick. There are, I presume, two layers with a space in the middle. I'm not sure how practical it would be, however, to get piping in there, and since it's exposed brick only on the outside, I think I'd probably end up heating the area outside the house next to the brick more than the interior of the house.

Larry Weingarten

Hi, I mentioned panel radiators as a way of getting heat into the rooms without major remodeling. Perhaps a reflective surface or insulation between radiator and brick wall would encourage the heat to stay in the living space a bit longer.
Yours, Larry

Jamie Hall

Well... I think @Larry Weingarten 's approach is a good one -- you are using the solar energy directly, as thermal energy. There are a number of different ways to go about doing this, of course, as well as a number of ways to store the resulting heat (several places of which I am aware simply use large, well insulated water tanks. Solid concrete walls or floors work well, too). But where this is a retrofit, I think you will be somewhat limited in what you can do.

I would never bet on the economics of solar photovoltaics. You are completely at the mercy of political whimsy, and what looked like a really great deal today can turn into a complete financial catastrophe, with a stroke of a governor's or premier's pen.

mikeg2015

I wonder if you could use fin tube baseboard and create a DX system using a inverter mini split outdoor unit. You’d have to use R134a to get vapor temps up to 160f in colder weather. Should be able to use the inverter to target a certain vapor temp and the EEV automatically controls superheat. Can use 1/4”’liquid line for the returns and 1/2” vapor lines for supply. All flared connections.

Leonard

Other issue with solar PV is heard have to clean the dust off them occasionally for optimum performance. Not to mention the snow.

I remember in Worcester Mass one year at school it was cloudy and we did not see the sun for 30 days STRAIGHT in ~ January 1977

Was a techie school (WPI) so a thermal solar collector was installed on roof for DHW experiment/project. Seem to remember they had it at a very steep angle ~ 45 degs , don't remember snow collecting on it too much but it's been 40 years. Tall roof , 2.5 stories , so don't think anyone went up there to wipe off snow. Had radiators to dump the heat in summer when dorm buildings weren't occupied.

Leon82

I just saw a video on Facebook of a panel cleaning contraption two guys were going row by row watering the dust off. That's going to be hard on a two story roof

FuriousGeorge

I'm not sure if the city will let me install a geothermal heat pump, however I like the idea of using it to assist the forced air AC as well.

If I'm not mistaken, it's not difficult to convert a modern steam boiler to forced hot water, so the existing piping is the main principal unknown.

Jamie Hall

OK. Let's start all over.

I presume, though you have never actually said so, that the existing heating system is steam? If so, by far your best bet -- in terms of overall fuel efficiency or reducing your carbon footprint or whatever (never mind comfort for the occupants and low heating bills) -- is going to be to put in a modern steam boiler, running at 85% efficiency (which they do) and making sure the steam system -- venting particularly -- is up to par.

Unless you are on a very large lot, geothermal with a heat pump is likely to be a non-starter (there are ways to do it on a small lot, involving deep wells... but... $$$). Air to hot water heat pumps are pushing the envelope pretty hard, particularly as if you want to keep the existing radiators you're going to have to run hot -- and they don't like that. Air to air heat pumps do work well enough -- but there is the expense (and environmental cost) or ripping out all the piping and putting in nice big ducts all over the place. And with very few exceptions none of them are particularly good at low temperatures, in terms of COP -- and if your electricity is from the grid, you have to be at at least 3 for the COP to beat a straight fuel fired local boiler.

I'm not trying to discourage you from installing photovoltaics or solar heat panels, if it makes you feel good. Just trying to point out that in terms of comfort, cost -- and saving the planet -- you'll do better to upgrade your existing steam system.

Leonard

Heat pump...
As you increase temperature spread between heat source and fluid your transferring heat energy to the COP will drop. (That heated fluid can be air, water or steam.)

Suspect these heat pump systems are best when your heating building air directly and getting that heat from relatively warm ground water ( maybe 45 degs) rather than cold winter air (0 degs).
With cold air you can also have the evaporator icing issue, and required defrost ( usually high KW electric heat strips)

Since would have lower COP I would not have considered steam heat supplied by heat pump. It makes you use more energy to get fluid up to a excessively high temp, only to let it fall back down. I have not run the COP numbers.

Why won't city let you install geothermal well? Are a few different ways to do it: pump water in/out of well(s) , drop tubing loop to bottom of well and cement it in. Another way is to bulldoze ground, lay out long loops of tubing then bury them ~ 10 ft underground

FuriousGeorge

Jamie Hall said:

OK. Let's start all over.

I presume, though you have never actually said so, that the existing heating system is steam? If so, by far your best bet -- in terms of overall fuel efficiency or reducing your carbon footprint or whatever (never mind comfort for the occupants and low heating bills) -- is going to be to put in a modern steam boiler, running at 85% efficiency (which they do) and making sure the steam system -- venting particularly -- is up to par.

The current system is a 12 year old steam boiler. The owner will have to pay for all three units. Unfortunately, I can't change the name of the thread, but per previous suggestions, the ROI for various non-PV solutions is what I'm investigating now. Anything with an ROI in the 20 year range would be acceptable.

This would necessitate changing the steam boilers to forced hot water, and likely changing out the radiators, though I don't know that yet.

As you point out, a PV array would need to be impractically large to provide enough KWh for heat. Instead, I'm doing the math for 1000 ft^2 of PV/Solar Thermal.

In terms of potential output: assuming 300 W/m^2 over 6 hours at 40 latitude on a sunny day in the winter, a 1000 ft^2 roof on a sunny winter day at 50% efficiency would provide about 2/3 of the necessary energy. Those numbers appear to be from some college lecture course material. This assumes 15 therm/day of consumption for the building, and of course the sun is not always shining. I'm just running rough numbers.

Obviously, another source of heat will be necessary, and NG can always be used as a last result.

The laws for this state affect the calculus. They are in the process of becoming more renewable friendly, but as of now, the more energy you consume, the more you are allowed to make and get credited for. E.g. if a building uses 500 KWh per month on average, then it can be credited for 500 KWh of production beyond what it has used. However, if you do inefficient things that cause you to consume 1000 KWh, then you will be allowed to cover that consumption and sell back 1000 KWh. Also, the Utility Co will also finance the project, and allow you to use the renewable credits to repay it. The more you make, the faster you pay it off.

It's not that I want to start a micro utility, but if the energy is free after the installation, it can be put to work, and is preferable to NG. I'm not married to any of this. Any renewable way to make hot water is acceptable, provided the numbers make sense. As discussed previously, renewable ways of creating steam are logistically prohibitive.

FuriousGeorge

Leonard said:

Since would have lower COP I would not have considered steam heat supplied by heat pump. It makes you use more energy to get fluid up to a excessively high temp, only to let it fall back down. I have not run the COP numbers.

Sorry for the confusion. I forgot to mention that the existing heat is steam, but after sizing the PV array needed for this, and given the better efficiency of solar thermal, it seems that forced hydronics would be necessary.

Leonard said:

Why won't city let you install geothermal well? Are a few different ways to do it: pump water in/out of well(s) , drop tubing loop to bottom of well and cement it in. Another way is to bulldoze ground, lay out long loops of tubing then bury them ~ 10 ft underground

I don't know for sure that they won't. I've read that there are some considerations in terms of ordinances and municipal infrastructure in general, but don't know anything specific about my situation yet.

Leonard

Guessing issue is setbacks from property lines.

Maybe also setback of well from septic field ...,,,,maybe they are ASSUMING its a drinking water well or may be one in future. I'ld ask for details.

nibs

Am an aficionado of PV, got my first panel in 1981, and have quite a few now.
IMO you are more likely to benefit financially by buying shares in a good solar farm or manufacturer. Unless you live in the sun belt. I expect that if the utility lines come to your house, you cannot beat their energy price.
I do not try and replace grid power, but use PV on my RV's and to power the 12 volt pump on my hot tub as well as providing all the power that my electric garden tractor needs from its 300 watt PV panel which serves as a rain and sun shade for the operator.
A rule of thumb which I use is that for every $100 dollars you spend on PV you need to spend $200 on batteries.

FuriousGeorge

nibs said:

Am an aficionado of PV, got my first panel in 1981, and have quite a few now.
IMO you are more likely to benefit financially by buying shares in a good solar farm or manufacturer. Unless you live in the sun belt. I expect that if the utility lines come to your house, you cannot beat their energy price.

...

A rule of thumb which I use is that for every $100 dollars you spend on PV you need to spend $200 on batteries.

I wouldn't be trying to replace the grid. Batteries aren't necessary, as the utility will buy excess credits at the retail rate, on an annual basis. You determine when this annual contract starts. Excess credits made when consumption is low can be used months later, when consumption is high, and that's your battery.

While you could get a smart inverter/battery setup to store energy when there is overproduction preferentially to backfeeding, there is no real need to, as you get the retail rate.

They public utility also offers financing. Between that and the federal and local governments the project is mostly financed or funded by grant, and excess production can be used to pay all the financing, which incentiviszes larger installations (otherwise you make up the difference with cash at the end of the year).

All this is the case because, as you point out, otherwise it would not be viable, so the state government forces the public utility to do it. An ever growing percentage of our energy must come from renewables. These laws, as they are intended to do, change the cost-benefit analysis for the better.

Once paid off, you get free energy on a three family unit that you'd otherwise be paying for, for decades with minimal maintenance,
which -- even if you don't produce a single credit -- is still a better investment than stock in a renewable energy venture (which, some would argue, is probably rarely a good investment).

nicholas bonham-carter

What sort of steam system is now in place?
Often grants, and low-interest loans from public bodies come with strings attached. Any solar powered system will need ongoing maintenance, perhaps to the tune of wiping out the free energy savings.
If the steam system has been adequately maintained, the lifespan of the boiler might be another 20 years.—NBC

Jamie Hall

I'm afraid you've hit a hot button. Any time someone says free energy I get upset. First place, solar panels have a finite life -- comparable to a good boiler. Second, they are environmentally disastrous to make. Third, they require constant maintenance to maintain output. Fourth, if they depend on the grid for those credits, may I ask where the grid gets its power from? At what efficiency (around 40%)? Fifth, if your "free" energy is being subsidized by the state or the utility, where does the subsidy come from ( and this is where I object: it comes from me, good buddy, and I'm not interested in paying for your good vibes)?

The environmentally and socially responsible approach for you to take, @FuriousGeorge , would be to properly maintain and upgrade your steam system and, more particularly, the heat loss of your structure.

Mind, I'm not opposed to reducing energy use. I'm not opposed to trying to be more environmentally responsible about it. I do object to a lot of the renewable energy work -- at least what I see around here: good farm fields taken over by solar grids; the best hawk soaring location in New England ruined by a wind farm (no hawks there now); native americans forced off their land by massive hydroelectric facilities which will never pay... the list goes on.

End of rant.

hot_rod

Mind, I'm not opposed to reducing energy use. I'm not opposed to trying to be more environmentally responsible about it. I do object to a lot of the renewable energy work -- at least what I see around here: good farm fields taken over by solar grids; the best hawk soaring location in New England ruined by a wind farm (no hawks there now); native americans forced off their land by massive hydroelectric facilities which will never pay... the list goes on.

No doubt there is an environmental cost to any and all energy source. Recently released EPA stats indicated contaminated water around all the US coal sites.

As for wind generators and PV arrays on farm land, they exist because the owner of the land get very generous rent, and can still farm up to the base of the towers.
Properly mounted, shade crops can be grown under PV arrays.

Agreed wind take a toll on the birds. Wind surpassed coal last year for energy contribution, I expect that will continue.

Probably some farmers doing better with wind lease $$ when compared to trying to sell their soybeans that are tariffed out of the market

FuriousGeorge

Jamie,

For the record, I'm not a 'solar fanboy'. I'm doing a cost benefit analysis. I haven't always wanted PV cells. I've never wanted them.

I can understand not wanting to pay for other people's subsidies. I know the feeling. My state is one the largest net producers in the economy, but has no fossil fuel reserves. It seems to me that the politics against the renewable subsidies that can benefit me generally come from the states who are, on net, taking from the economy.

That's despite the fact that fossil fuels have been subsidized for a century, at least, to the tune of billion per year today, despite being one of the wealthiest sectors already, and that's nothing to say of the industry's lobbying power.

Ultimately, I accept that we subsidize coal, despite the fact that the heyday of coal was two centuries ago. Speaking of all the subsidies for renewables, I accept that we subsidize ethanol, although we do it just for the corn farmers, and the heyday of corn farming was 20 centuries BC. On top of this, we do it to almost no end. Who does it really benefit and how much vs ripping the band-aid off and subsidizing something else? Do you remember your grandma saying things like "He's as rich as a coal miner", or "she lives like a corn farmer"? Unless she was really sarcastic, I doubt it.

I'd say not to take subsidies away from those states (or raise their taxes or cut their federal support) because, if for no other reason, it would be on-net bad for the country, despite being good for my state. If you wan't a more selfish reason, these subsidies might indirectly help us one day. It's better to accept that part of what I work for, and what we collectively as a state work for, goes to them, and they should have most (not all) of the say on what they spend it on. I realize not everyone thinks this way.

All that mess aside, I always took it for granted that if every watt of power generated by coal was gradually replaced by PV, it would be a net positive. I haven't looked into that specific point, but for better or worse the economics of this have already worked themselves out, and given time it's a done deal. The cost of producing solar is half of coal and dropping. Energy density and storage tech are both improving rapidly, and decentralization (!) helps with that. Decentralization is also good for national security. The technologies we use to generate power from turbines and combustion are bumping up against their max efficiency, barring some futuristic breakthrough like long-distance room-temperature superconductors, which would benefit all energy production. Meanwhile, we are far from our ceiling with renewables.

It is sad about the falcons, and wind turbines aren't quite as pretty as dutch wind mills, but have you driven by (or smelled) a coal plant lately. The fossil fuel industry has centuries of human and environmental mishaps associated with it. Ducks don't like oil slicks.

Yes, there are costs involved with producing your own power. "Free energy" was probably a bit too flippant. Semantics aside, after the human cost of maintenance, which does increase exponentially with my time, and the actual cost of maintenance, there is energy that can be put to use that there would not otherwise be. A reasonable actor might determine after the costs are considered that there is still a net gain ("net positive energy"). Economy of scale (e.g. multifamily capacity) can help with this further.

FuriousGeorge

With respect to heat: one of the benefits of steam that I don't think has been mentioned, is that it feels really nice. My current residence has baseboard, and I noticed the difference right away upon entering.

I'm realizing that geothermal pumps won't be getting the water to 200 or 180 F. Instead, 160 F is the max, and that's already at a low COP. The radiators having been sized for steam, and there will probably be a comfort drop off if I don't add more. I'd have to investigate the particulars of that. (There is a lot of radiator in the living rooms, and I would not be surprised if that area tended to get too warm.)

Solar Thermal can offset that a fraction of the time, and even get up to 200 F, but from what I've read they have historically been a maintenance nightmare, and tend to fail catastrophically when they fail. All this probably adds up to using a good amount of NG, or a lot of electric to make up the difference.

FuriousGeorge

nicholas bonham-carter said:

What sort of steam system is now in place?
Often grants, and low-interest loans from public bodies come with strings attached. Any solar powered system will need ongoing maintenance, perhaps to the tune of wiping out the free energy savings.
If the steam system has been adequately maintained, the lifespan of the boiler might be another 20 years.—NBC

I know it's 12 years old, and presume it is well maintained, if the rest of the of the property is any indication (not that it necessarily is).

I haven't read the fine print on the power company's financing offer, but I will be sure to. One of the main subsidies is the federal governments 30% program. There are a handful of state programs as well, and I believe some municipal ones. The purpose of this thread is more to get an idea of the scope, and work forward from there.

With respect to maintenance, with a multifamily home you usually have one unit be a superintendent (from that property or another if you have multiple).

Jamie Hall

Farmers get very generous rent for the solar arrays on their fields? Not in my state they don't. The rent I would get for a solar array on my best fields wouldn't be enough to pay the increased property tax, never mind make any sort of money (and it would be a big array -- somewhere around 10 megawatts). I've looked into it. I could run dairy cattle on the field -- but that's a losing game. I wouldn't be able to hay it any more.

Nope. Sorry...

Actually, though, I do realise that New England and downstate New York are sort of a special case, and that affects my thinking. With the forced closure of our nuclear plants, we have three choices: more fossil fuel power plants (natural gas, not coal), but that is limited by pipeline capacity which is politically impossible to increase; offshore wind, which may not have the ecologically harmful effects of wind turbines on all the mountain ridges (truth is, we don't know), or importing hydro power from Quebec -- which expropriates First Nations tribes from their lands for their big dams and reservoirs, with no compensation -- never mind flooding the free rivers in northern Quebec (and who cares -- no one ever goes there, and the First Nations don't count).

Perhaps, @FuriousGeorge , I am not a reasonable actor. I am, after all, an engineer by training and engineers are perhaps a little cautious. I do think that there are easily available and technologically and environmentally sound approaches to providing the energy we need, and not only that we need but that Europe and the third world countries need. There are countries which are pushing hard on these technologies -- although their safety standards are not really where they should be. It's a shame it isn't our country, but that's the way it is.

FuriousGeorge

Jamie Hall said:

Perhaps, @FuriousGeorge , I am not a reasonable actor. I am, after all, an engineer by training and engineers are perhaps a little cautious. I do think that there are easily available and technologically and environmentally sound approaches to providing the energy we need, and not only that we need but that Europe and the third world countries need.

@Jamie Hall

I'm sure you're rational, or you'd be a surrealist artist, not an engineer.

I'd posit that, for instance, electrical engineers would be more likely than the average person to have a solar array in their homes, if only because it would be less mystifying to them. I don't know that for a fact, however. If the opposite were true, it would give me pause.

Obviously someone (not me) has been installing them fairly frequently for about 10 years, given the drop in price. I'm not an economist, but my understanding is that people in a capitalist system can only be influenced by some sort of mass hysteria for so long, before in the end they return to being rational.

By that logic, and considering the cost of per MW of coal vs solar, and considering how few people work in the sector relative to solar, continuing to subsidize coal is what seems like the mass hysteria. Time will tell. Perhaps the future is a solar dystopia, and coal will save us.

Again, I'm not a solar fanboy. I find reading about biochar more interesting (though I guess that is solar). Maybe we agree on that.

Jamie Hall

For what it's worth, I'm not particularly keen on coal, either, and I find it particularly sad that Germany, to take one example, switched to burning lignite coal (the dirtiest there is) to pick up the base load power which renewables couldn't supply when they closed all their nuclear plants... but, that's the politics of it, not the science or engineering.

And I'd much rather use soybeans and corn to feed the world's hungry than to burn them. But that's political, too.

FuriousGeorge

@Jamie Hall

Coal works for my foil to solar because it's what the local power company uses.

I'm actually pretty bullish on nuclear, still, but I'm biased in that I always found it pretty cool. I think it can be done right. At the same time, I can understand why some people do not. We just had another melt down, and you can't plan for a subset of infinite possibilities. It's fun to try, though:

Since this has gone off the rails already, and I may as well start another, why don't they just put the reactor cores (which generate steam, and so I'm not completely off topic) underground, encased in cement with lead or something to keep the rays in?

If something goes more you level the above ground structure, put it in the hole, and backfill it with more cement and lead.

This way, you aren't trying to maintain a sarcofogous for all eternity, or inventing robots to extract the fuel in 20 years, while you spend billions to contain it in the meantime.

I guess it would get too expensive.

hot_rod

I am a bit of a solar fan boy, proud to say, thermo mainly. I have had thermal on all the homes I've owned for going on 40 years now. I currently have 5 thermal systems running on my property, an a small 1.2 KW PV to tinker with.

Drainback solar, basically an aluminum box with copper tube inside, will often outlast the roofing materials it gets mounted on. Usually it gets pulled off to re-roof, but not often reinsta

I've never hosed them down Thermal works on overcast days also. Full sun is considered 317 btu/hr./sq. ft. striking the absorber, days with less still provide some energy. Simulations are easy to run to see what your system would supply.

A low temperature distribution system if what you need to consider to match with thermal. That is plenty doable on new and remodel applications, SWT below 120F ideally.

Realistically 15- 20% of a heating load covered by solar, maybe a bit more in sunbelt states. DHW loads are easy picking with a small thermal array, 50% or more is obtainable in most areas.

Here is a journal with some ideas for solar assisted hydronic heating systems.


https://www.caleffi.com/sites/default/files/coll_attach_file/idronics_6_0.pdf

Jamie Hall said:

Farmers get very generous rent for the solar arrays on their fields? Not in my state they don't. The rent I would get for a solar array on my best fields wouldn't be enough to pay the increased property tax, never mind make any sort of money (and it would be a big array -- somewhere around 10 megawatts). I've looked into it. I could run dairy cattle on the field -- but that's a losing game. I wouldn't be able to hay it any more.

Nope. Sorry...

Actually, though, I do realise that New England and downstate New York are sort of a special case, and that affects my thinking. With the forced closure of our nuclear plants, we have three choices: more fossil fuel power plants (natural gas, not coal), but that is limited by pipeline capacity which is politically impossible to increase; offshore wind, which may not have the ecologically harmful effects of wind turbines on all the mountain ridges (truth is, we don't know), or importing hydro power from Quebec -- which expropriates First Nations tribes from their lands for their big dams and reservoirs, with no compensation -- never mind flooding the free rivers in northern Quebec (and who cares -- no one ever goes there, and the First Nations don't count).

Perhaps, @FuriousGeorge , I am not a reasonable actor. I am, after all, an engineer by training and engineers are perhaps a little cautious. I do think that there are easily available and technologically and environmentally sound approaches to providing the energy we need, and not only that we need but that Europe and the third world countries need. There are countries which are pushing hard on these technologies -- although their safety standards are not really where they should be. It's a shame it isn't our country, but that's the way it is.

I was talking about wind on farmers field, not PV arrays, I should have been more clear, maybe.

FuriousGeorge

@hot_rod

You're a DIYer, I take it?

I came in to this thread thinking thermal was not an option, because I didn't know much about it, and now that I know more I'm thinking that it isn't again.

There have been some terrible write ups on available systems. It seems like they require a ton of maintenance. Apparently, when they fail, they fail catastrophically in many cases, with panels warping or ruptured pipes and leaks.

The 30% credit can be applied here, if it makes sense overall, but not for something I create. I'm not that good with an arc welder anyway, sadly.

FuriousGeorge

I'll add to my previous comment that using the same roof space for both applications is enticing, but I have you to determine if overheating it can break both.

Leonard

I think you really have 3 somewhat separate subjects going on here. Whether to use solar thermal, use solar PV for utility cost reduction , and best/cheapest way to heat house..

Thermal solar.....Got to plan for collector overheating in summer heat wave, sun doesn't shut off just because collector water gets to boiling and DHW tank is happy and pump is off or failed. Some collectors are designed better than others to take this heat

Ideally safety system should be passive ( not rely on pumps for cooling) System should have a have a relief valve, be nice if that overflow goes to a barrel to recover $$ antifreeze.

DIY obviously helps with install cost. In Maine a relative put in 5kw PV solar , feeds excess back to utility , net metering. they figure ~ 15-20 years break even. Her father was a carpenter and did the physical install. Electrician he knew did wiring at a reduced price rate. Roof was metal, so no re-roofing in 20 years.

My biggest issue with hers is each panel has a micro-inverter. So if it dies have to go on roof to lift panel to replace it. I'ld prefer ONE in-house central inverter, that during utility power failure can isolate house from utility and let inverter make 120/240 for the house (during daylight, use gen at night). Also MUCH easier to replace if dies.

PMJ

I think it is a mistake for government to steer incentives such that any energy source gets abandoned. While it is clear that many folks (especially politicians) do believe they know which energy sources are the best for all of us and our future; common sense alone advises us that they really don't. No one does.

Engineers will continue to improve and advance whatever they work on including things like coal and nuclear. The only thing certain to stop advancement in something is stopping the use altogether. This I would advise against. Like the stock market, the advice always ends up get some of everything because no one knows how it will play out - even in the short term. If anyone wishes to ponder a potential national security issue consider a major breakthrough in something that we didn't know anything about because we had abandoned all work in that area. Not good. Real experience fades quickly. Much better to keep a hand in everything.

I see nothing available today that would save enough on my steam heat bill to replace anything. If I were doing the math I certainly wouldn't rely on any goverment incentive or a utility promise to buy power from me over the long term when evaluating anything. I also would stay away from ideas like no maintenance. Everything has a maintenance cost. The newer the technology is the less is known about what that actual cost is. From what I can see, with all the sensors, pumps, blowers, controllers, inverters and more that are necessary now, I'm still watching for something that has any chance to beat the ongoing maintenance cost of a good steam system.

FuriousGeorge

Leonard said:

I think you really have 3 somewhat separate subjects going on here..

Yeah, my OP was dumb. "Three somewhat separate subjects" is my estimate, if you don't count the politics.

Jamie Hall

Amen, brother @PMJ , Amen!

hot_rod

Leonard said:

I think you really have 3 somewhat separate subjects going on here. Whether to use solar thermal, use solar PV for utility cost reduction , and best/cheapest way to heat house..

Thermal solar.....Got to plan for collector overheating in summer heat wave, sun doesn't shut off just because collector water gets to boiling and DHW tank is happy and pump is off or failed. Some collectors are designed better than others to take this heat

Ideally safety system should be passive ( not rely on pumps for cooling) System should have a have a relief valve, be nice if that overflow goes to a barrel to recover $$ antifreeze.

DIY obviously helps with install cost. In Maine a relative put in 5kw PV solar , feeds excess back to utility , net metering. they figure ~ 15-20 years break even. Her father was a carpenter and did the physical install. Electrician he knew did wiring at a reduced price rate. Roof was metal, so no re-roofing in 20 years.

My biggest issue with hers is each panel has a micro-inverter. So if it dies have to go on roof to lift panel to replace it. I'ld prefer ONE in-house central inverter, that during utility power failure can isolate house from utility and let inverter make 120/240 for the house (during daylight, use gen at night). Also MUCH easier to replace if dies.

Solar drainback use plain water, they drain when the load is covered, very simple, low maintenance. It's possible to us PV powered circ, but with ECM technology the pump operating cost is minimal. If power goes out, the collector drainback.

On one of my buildings I have a 1978 vintage Revere Copper collector still chugging away.

hot_rod

FuriousGeorge said:

@hot_rod

You're a DIYer, I take it?

I came in to this thread thinking thermal was not an option, because I didn't know much about it, and now that I know more I'm thinking that it isn't again.

There have been some terrible write ups on available systems. It seems like they require a ton of maintenance. Apparently, when they fail, they fail catastrophically in many cases, with panels warping or ruptured pipes and leaks.

The 30% credit can be applied here, if it makes sense overall, but not for something I create. I'm not that good with an arc welder anyway, sadly.

I'm a plumber, been installing solar thermal and radiant systems for quite a few years.

The failing system that you are reading about may be cheap import evacuation tube collectors, they brought a bad rap to the industry.

AET, Heliodyne, and Sun Earth have been manufacturing quality flat panel solar collectors in the US for 30 years or more.

On the fringe is high temperature ST that can heat and cool. my friend Bill Guiney has been heating and cooling buildings with ST for years.

http://articsolar.com

FuriousGeorge

PMJ said:

Engineers will continue to improve and advance whatever they work on including things like coal and nuclear.

@PMJ

Any advancement in the efficiency of producing electricity from nuclear or petrofuels in a centralized location is likely to benefit all energy production. There is no breakthrough on the horizon that will solve the problem of the inefficiency of moving electricity over long distances. With respect to gas turbines, I'm sure everyone here remembers $100+/barrel oil, and the lack of major breakthroughs in vehicle efficiency since then (unless you count electric batteries in our cars and houses, obviously, which should be a red flag).

If we really want to make coal and nuclear more efficient, the best thing we could do is use them to make electricity in our basements. This also has myriad benefits in terms of redundancy, fault tolerance, national security, scalability, safety, etc, etc, not to mention most of all: efficiency.

Say what you want about the folks with PV cells and solar water heaters: they put their money where their mouths are. I don't see anyone setting up CHP coal boilers in their houses. There have been many community-scale nuclear concepts, but no buyers, anywhere. My guess is that the reason is that these technologies are better suited for some other place, far from the point of consumption.

That said, I'd run a steam boiler on coal in my basement for CHP, at least for a while, if it came in some low maintenance kit (edit: and I had access to coal). It seems like a fun thing to do, and it would be much better for the planet compared to the status quo. How many people are like me, though?

I'd mention Stirling Engines, but this is the steam room.

PMJ

@FuriousGeorge ,

You seem convinced then that no significant breakthrough in power transmission is possible. I count nothing out in any area. I say I can't pick where the next breakthough will occur any more than I could pick a single stock to put all my money on. I am very sure our government can't pick it either.