Zero Energy Case Study Report

jp_2

BIG thanks to Kevin

kevin, lots of disagreement here, but we are all talking and thinking about this subject.

thanks for posting.

scott markle_2

b

Hydrogen is not a great portable fuel because it's so difficult to contain. "economical" fuel cells? I'm sorry to always play the sceptic but I think there are a lot of people whipped up into a subsidized alternatives fantasy these days. Think of the server farms humming all night to keep our little chat alive. We live in a energy intensive economy. I believe we must reform our appetite and expectations with regard to energy instead of projecting false hopes on alternatives. As far a mandating ZEH's I think your getting a bit carried away. I know we can be smarter about the way we site houses, but unobstructed southern exposure is not universally available. Trees have tremendous value too. Do we give a kw value to the shade a tree provides. Do we subtract from our net metering equation the "cost" of that treeless exposure. When I drive around these days I often look a houses with a eye to solar suitability, I'm struck by how few houses are truly good candidates.

Gas is transported over continental distances and through towns and cities without any of the transmission losses that effect electricity. Gas is an ideal heating and cooking fuel. Why convert it to electricity (with all the thermal losses involved) instead of using those btu's directly and efficiently at the point of use?

jp_2

Rural areas

scott you can't forget about the rural areas that have electricity but no natural gas lines. lotta places around here have no gas line, as I'd guess in the upper midwest, dakotas,montana,wyoming......

gas isn't quite free to transport, it does need to be pressurized, it too has line losses.

but i have to admit, I DO like cooking with gas.

realolman

I agree

And there are also a bunch of pretty sharp cookies on this site.

thanks... keep er comin.

Kevin_in_Denver_2

Heating systems and utility rates

To learn more on the topic, Check my blog:

Kevin_in_Denver_2

system design vs. utility rates

For a little more on the subject, see
http://greenbuildingindenver.blogspot.com/

Bob Gagnon plumbing and heating

I agree with Metro Man

I think radiant heating will make solar hot water systems more efficient and worthwile. And it's a lot easier and less expensive that a lot of people think. You will only need a small radiant panel and a second larger storage tank to heat a superinsulated house. Playing around with solar on my house mirrors some of the same issues as this house. I have a 120 evacuated tube collector heating a 200 gallon tank, and a lot of time the collectors can't collect anything because the tank is running 120- 150 degrees and the collectors can't make water hotter than that. Yet my homemade flat plate collector, tied into a 1500 gallon tank, that I use for radiant heating, will collect low temperature BTU'S, 80 to 100 degrees, all day long. I also agree that if we design these systems properly they can be trouble free for decades- like a simple forced hot water system. We all know that water is the most efficient and comfortable way to deliver energy, it's up to us to get it done. Soon I'll be posting a simple space heating design on a new thread, that would make solar hot water 50% more efficient than the way we are doing it now. I would appreciate your thoughts on any improvements that we could make to this system.
Thanks, Bob Gagnon

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Kevin_in_Denver

More PV vs. Thermal

And thanks to all for this lively discussion.

Bob, you're right, solar thermal can be relatively simple and definitely cost effective.

I just happen to believe that Photovoltaic cost effectiveness is improving much faster and has further to go than solar thermal.

Here's the quote that really got me thinking about and investigating this:

“But for the mean time, at least here in Colorado where the utiity is REQUIRED to buy back excess electrical production, I'm thinking PV solar makes more sense for the world as a whole. If during the summer months, the dwelling to which the array is attached can not use the electricity being produced by the PV system, it goes back into the grid, helping to offset the demand imparted to the grid from cooling loads.” - Mark Eatherton

Bob, you're describing a solar thermal system that has pumps, tanks, copper, glass, aluminum, controls, sensors, heat exchangers, o-rings, valves, potential leaks, pesky high temperatures, potential corrosion, etc., etc.

I don't like to pay money for any of the above if I can avoid it. I think I can avoid it with a combination of PV and electric resistance heating in superinsulated new construction. Air conditioning is easy and cheap in Denver with a swamp cooler.

Bob Gagnon plumbing and heating

I still like thermal

All the potential problems you mentioned we deal with all the time. Potential leaks, pumps, valves, corrosion are problems we deal with all the time. A solar system is the same as a forced hot water system and we know if we buy quality stock, pumps, expansion tanks, valves, and properly install them in a well designed system, we might go decades without having a problem. And any good plumber testing the new system to 100 lbs. or more will not have any leaks. I'm not ready to give it up to the electricians yet, it's up to us plumbers to make thermal systems as efficient as we can. Solar Today Mag. reports that in Europe they collect almost twice as much energy with solar thermal, than PV and wind combined. That should tell you something. Hopefully we will be working hand in hand with the PV guys soon anyway, In England they are working on combined PVT panels. Photovoltaic and thermal combined. It seems that PV panels produce more electricity when they are kept cool, and I expect that they might last longer if water is running through them also. How great will it be when we can work together and put panels on the roof that produce electricity and hot water. In ther meantime I think those of us familiar with water should work to make these systems as efficient as we can. PV is easier, no doubt, but Thermal is definately better. Thanks, Bob Gagnon

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Metro Man

Life after rebates

If we are talking strictly $$ then currently the average PV system's payback or break even point is about 16 years without any service. I am assuming a $10/ watt cost which is about the norm. When those expire double that number. Yea it's cool that this thing produces power that can be fed back to the grid and etc.... Wouldn't it be a better idea then that you buy your PV system and install it is in Xcel's back yard? That way since you are now a utility you could go into the electric businesses, get a check from the power company, and retire. Buy lots of PV panels and you could power your own city! Your utility controlled and maintained system would always have the correct angle, 0 shade, mounted on the ground, and easily serviced. Look at some of the installs going in. Can't fit it on the south side lets put some PV on the east then some on the west for morning and afternoon sun..... What the ?????

And therein lies the difference, solar thermal systems store energy in the home. When you look at that annual power bill heating (at least in Colorado) is always by far the most expensive followed usually by hot water.. then electricity. One little circ pump suckin' 140 watts can generate 1,000,000 BTU's per day or more.... not bad in my book.

These last 10 years or so have been great with the technological advances in radiant heating systems. These systems tie in very well with the temps that a thermal system can deliver. The super low loads of a heavily insulated and passively designed new home allows a solar thermal system to contribute more than ever. Never would of thought of installing a 80 MBTU in a 6000 square foot home b4. I'm still waiting for the boiler co's to come out with 5 - 75MBTU units.

Homes that would have required 400 sq ft of collector area are coming down to half of that. Mostly because codes are requiring tighter homes. How tighter can we go? I think quite a ways. I can see the technology get to where a full blown solar thermal heating system size decreases to that of a large SDHW system. Storage could be built into new homes for heating and cooling. Those are the kinds of homes we should be building.

As far as pumps and o rings and etc.. Like Bob said if you install the system correctly with quality components you will go years without problems. Don't think because you can't see the diodes, transformers, IC's, wiring, capacitors, and etc... hidden inside that slick box called an inverter that they will run indefinitely. And who's going to service that thing? You can only go so far in your troubleshooting (been there done that) then you yank it off the wall send it back to China or ??? have the company who made fix (if they can) then they get her back to you. Cost to replace that is around 25% the cost of the system. I'd rather buy a taco or grundfos.

But..... inverters like pumps and o rings are always getting better.

Just to show that we aren't totally biased I've including a shot of one of our thermal and pv projects.

My 2.75c

Metro Man

Metro Man

> All the potential problems you mentioned we deal

> with all the time. Potential leaks, pumps,

> valves, corrosion are problems we deal with all

> the time. A solar system is the same as a forced

> hot water system and we know if we buy quality

> stock, pumps, expansion tanks, valves, and

> properly install them in a well designed system,

> we might go decades without having a problem. And

> any good plumber testing the new system to 100

> lbs. or more will not have any leaks. I'm not

> ready to give it up to the electricians yet, it's

> up to us plumbers to make thermal systems as

> efficient as we can. Solar Today Mag. reports

> that in Europe they collect almost twice as much

> energy with solar thermal, than PV and wind

> combined. That should tell you something.

> Hopefully we will be working hand in hand with

> the PV guys soon anyway, In England they are

> working on combined PVT panels. Photovoltaic and

> thermal combined. It seems that PV panels produce

> more electricity when they are kept cool, and I

> expect that they might last longer if water is

> running through them also. How great will it be

> when we can work together and put panels on the

> roof that produce electricity and hot water. In

> ther meantime I think those of us familiar with

> water should work to make these systems as

> efficient as we can. PV is easier, no doubt, but

> Thermal is definately better. Thanks, Bob

> Gagnon

>

> _A

> HREF="http://www.heatinghelp.com/getListed.cfm?id=

> 331&Step=30"_To Learn More About This

> Professional, Click Here to Visit Their Ad in

> "Find A Professional"_/A_

Kevin_in_Denver

Hybrid PV and thermal roofs

Dawn Solar already offers just what you are describing. I like it a lot.

scott markle_2

dawn solar

Kevin, Coincidentally I was just looking at the dawn stuff, I got there indirectly via your blog.

Well for one think I'm suspicious of the longevity of pex within this sort of demanding environment. I know that a standing seem roof undergoes a lot of movement and I would imagine that these instals would require very close attention to preventing abrasion of the pipe. Seems like a nice looking swimming pool heater. This is an unglazed collector, and it will have a very limited seasonal window of operation, at least in NH. The case study video impressed me as being a creative waste heat recovery project more than a solar project. Also the idea that solar should be unseen seems kind of limiting given the imperative of our energy situation. Form follows function is a my own belief as far as architecture and aesthetics.

Also pex in solar? not exactly permitted is it?

I think a galvalume roof that reflects heat back up to a tube collector is a nice arrangement. Seems like the sputtered glass type with the 360 deg absorber might be very good in this situation, space the tubes a bit less densely to optimize this bonus reflected energy.

Kevin don't give up on thermal, While the electric church is alluring we need to look at the whole picture, Even if Mark Eathron supports your conclusions. Smart guy to be sure, but He's into electric heated windows! not my idea of progressive energy management.

Metro Man

solar

Metro Man

life after rebates

The payback for a PV system is currently about 16 years with rebates. $10 a watt installed (about the going rate) Double that without rebates. Slap some PV on your roof and might get a check from Xcel at the end of the year. But at what cost and is this the way we should be approaching saving energy? The system in the report was a 4KW... $40,000 for electric? I think a better idea would be to buy your pv system and install it in Xcel's back yard. Since being a electric producer is the main goal. The site would be perfect, closer to the main grid, panels would have no shade, everything is facing south, maintenance would be on a regular basis. Look at some of the installs going on now... not enough south roof, we'll just stick some on the east and the west so these operate for 2 or 3 hrs........... what the ????. Seems like a waste to me. After the rebates are over where will we be? We would have designed our homes around electricity because that was the easiest cheapest way to get a return on our investment.... oopps!!!

This is where solar thermal will always have the advantage. We can store produced energy in the home wether we use a tank, concrete walls, or???? As these homes get tighter and tighter solar thermal systems can get smaller and smaller. Using super insulation, passive design, and state of the art radiant heating technology solar thermal system can produce a considerable amount of energy for heating and cooling. The cost ......running a 140 watt or so pump to produce 1,000,000 btu's per day or more. Not bad in my book.

Yes these are mechanical systems with pumps, o rings, valves, controls and etc.. but as Bob said using state of the art components and proper designs will ensure years of trouble free operation. Don't think that the slick little box called an inverter will never fail. Open one of those up and look at the transformers, IC's, diodes, fans, capacitors, boards and etc... You can only go so far trouble shooting one of these (been there done that) until the rep says send it back. Pack er up and send back to China or ??? If you end up replacing the entire unit your looking at about 25% of the cost of you system parts. Ouch... rather buy a taco or grundfos any day.


Inverters have come a long way.... but so have solar thermal and hydronic systems.

I think we should be looking at lowering the loads of our buildings.. This is where the research monies should be spent. 20 years from now maybe we'll be able to heat and power a home with a candle and a AA battery.

My 2.75 c

Metro Man

jp_2

ME's statement

i think he has changed his mind a bit on that statement?

when you look at spending $15,000-$20,000.00 on a systems and the constant pay back is a couple of dollars a day, the idea of graciously providing the neighbors with power looses its appeal. fine if you can get 20-30% of the population doing it, but whats the point when the percentage is well under 1%.

to me collecting energy without storing it seems like only half a system. plus without storage, your collection system(PV's) needs to be much greater, and theres where all the money is. don't see it as a smart system.

Kevin_in_Denver_2

pv cost correction

My 3.3 Kw system was $27k, but $12k after rebates

Bob Gagnon plumbing and heating

It just seems simpler and more efficient

To just heat the water. Sure we could make electricity with the PV panels and then use the electricity to heat our water, but it seem like it is a lot less efficient that way. We have to have hot water for our showers, we would like to have 90 degree water, and use radiant to heat our superinsulated houses. My gut instinct tells me thermal, it's all about the water. Thanks, Bob Gagnon

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Metro Man

Get hot from the sun...

Yep... sun is hot, thermal collectors get hot. PV hates hot. In fact PV works best on a clear cold sunny day. You should size your PV system's wiring for around -40 ambient in the Denver area.

Best solar to electricity conversion that I have seen is in Australia. Lots of computer controlled mirrors programmed to focus on a single "tower" that converts steam to electricity.

Cool... I mean hot!

BTW- Just to show that I do believe in both technologies here is shot of one of our thermal/PV job in Dever





Metro Man

Metro Man

Get hot from the sun...

Yep sun gets hot... solar thermal gets hot. PV hates hot. PV works best on a cold clear day. In fact you need to size your wiring for a PV system for around -40*F around here in Denver.

Best system that I have seen for electric conversion from the sun is in Australia. Huge field of computer controlled mirrors to reflect on a steam generator tower.

Cool..... I mean hot!

Just to show that we do believe on both solar PV and thermal technologies I am posting one of our installs in the Denver area. Haven't flashed around collectors yet. 2.65KW system with 400 sq ft thermal area. Radiant Heated home with a 1000 gallon stainless steel storage tank.

Metro Man