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Old 01-25-13, 04:45 PM   #1
Blue Bomber Man
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Default New (?) Idea for dealing with summer cooling with solar panels

I've been a lurker for a long time and enjoy reading many different methods of reducing energy demand presented here at this site.

I'm currently working on buying a house and starting to anticipate various ways I can reduce my own energy usage. I hope to eventually completely replace my winter heating needs (along with domestic water) while also significantly cutting cooling costs during the summer time.

The basic concept is typical of solar thermal systems. Large outdoor collector coupled to a heat exchanger in a large thermal storage tank.

My thought is to have a dividing wall in the storage tank to allow for multiple useful water temperatures. In the winter time, the smaller section would be used for domestic heating, while the large partition would augment or replace the need for conventional heating.


The summer time I would circulate to the heat exchanger in the large partition at night to cool the partition down, and during the day the smaller partition would circulate for domestic hot water.

As I thought about the cooling aspect of this solution I worried about removing excess humidity from the living space. So I thought that using a small geothermal heatpump coupled to the storage tank (rather then ground loops) would allow for this possibility. It would also drastically increase the effective capacity of the storage tank as a greater range of temperatures becomes useful for cooling. Additionally it would increase the efficiency of radiating heating off through the collectors at night.


Another side benefit would be increasing the useful capacity for heating during the winter. Instead of needing 110-120 degree water to effectively heat a home I could further extract heat efficiently from the tank, once again increasing the capacity of said tank.

A bypass for the heat pump would allow for direct heating while tank temperatures were high enough.

Included below is a rough schematic of what I'm thinking of.

Would love to hear some thoughts on such a system, and if anyone has heard of using a heatpump in this fashion.

PS: I know I should (and will be) focusing on efficiency and insulation before implementing such plans.

Thanks for the feedback!

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Old 01-25-13, 09:01 PM   #2
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Quote:
Originally Posted by Blue Bomber Man View Post
...The basic concept is typical of solar thermal systems. Large outdoor collector coupled to a heat exchanger in a large thermal storage tank....Would love to hear some thoughts on such a system, and if anyone has heard of using a heatpump in this fashion...
Interesting idea, parts of it I've considered, too.

It would be very helpful, since you're proposing to work with solar, to know where you are located, also what kind of insolation (amount of sunshine per year) you can reasonably expect.

And maybe something about the house you expect to have.

Since you are working on buying a house, you should give very serious consideration to the suitability of it for solar. Over at Build It Solar, you should find many resources to help you with that.

And how the window are oriented regarding the sun, and of course the infiltration & insulation.


Look at this photo of houses in Freiburg Germany. Every house in this development (solar development) is oriented toward the sun... they are smart. In the background, you can see houses that ignore the sun... they are not smart. Almost all houses built today, ignore the sun. You want a house that by accident or by design, is oriented to take advantage of the available sun.

I don't know how the weather is where you live, if things are beginning to grow, but if you go for a walk in a natural area (not landscaped) you will see that the plants and flowers that are successful take advantage of the sun.

So, you need to develop that sense too. You need to think like a plant, and realize that for your idea to work well, your house needs to be properly oriented to the sun.

Good luck with your house hunting!

Best,

-AC
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Old 01-26-13, 02:58 AM   #3
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Thanks AC for the response,

I live in upstate ny and I have frequented builditsolar many times, most recently to use their solar site calculator. Attached below is the data out from Andy Shroder's site.

Regarding the house that I'm likely buying, it is situated due east to west orientation, with a large amount of south face wall, with a fairly decent amount of southern windows. There are no shading issues during the winter time, and likely none during the summer time due to the higher altitude of the sun.

I guess I would like a bit of help understanding the attached graph, obviously Im mainly concerned with winter capacity as I am attempting to design for much more then just domestic water.

Based on the winter average (red line) I see around .5-.6 kw-hr/(day*m^2)

1kw = 3400 btu, so roughly 4kw gives me 1 ton of heating capacity.....
so Im assuming that translates to 8m^2 is approx 1 ton, or ~90 sq ft.


Right now I dont have much idea of the heating demand of the place im buying, but obviously I will be focusing on reducing that first, however I build enough solar capacity to at least offset domestic water needs initially, then once I have a better idea of heating loads I could expand the tank and collector array.

Probably towards the end next summer I would begin to experiment with night time cooling to see what is practical and efficient.

I also attached a satellite picture of said property, bottom of the picture is due south.

I would like to save the south roof for PV down the road, and use the south walls for solar thermal/cooling.
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Old 01-26-13, 09:25 AM   #4
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Default Ideas for net zero home

Blue bomber man

Welcome to the site.

There are many good ideas made here. Alot of them on the cheap. Taking an old humidifier and turning it into a very efficient heat pump water heater. Making your own ground source heat pump from an old scrapped air-conditioner. This is what I had learned here. Now over at builditsolar, building your own solar hot water collector was a site I learned how effective it can be.
I've been very fortunate I'm living in a home that I had built. For the area I live our home has things that were not common here. We have a heated concrete slab and exterior walls that are insulated on the outside as well as the inside. As the construction was happening I included conduit run from utility room to roof for the latter installation of solar PV. as well as a recessed area in the floor for batteries. With these innovative items and future plans already part of the homes envelope it makes it possible my addition of solar water space heating keeping our house comfortable.
IMHO I think if your goal is to live in a home that is gathering energy from its surroundings it should be from the ground up.
To buy an exsisting traditionally constructed home and to retro-fit it in order to acheive a higher level of efficiency is near impossible

As you had mentioned your looking for a candidate home to apply your ideas. You may want to consider the home itself first.

Look around make plans and gather ideas, save some money. There are a few Net zero homes out there and you could build one to. Some are show cases of colleges and university engineering, others are actual homes people have though about and built.

I think its a great time in which we live.

Imagine you can build a home that can be illuminated and air-condition by energy you collected with your PV and or wind. Heat your house without burning anything. Just gathering heat left in the ground from the past summer and pumped in with a heat-pump you built and learned about here.

Randen
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Old 01-26-13, 10:36 AM   #5
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Great project and great roof.

I've been in Freiburg a few times for solar conferences and it is quite a sight to see the things they do there that we only dream of here.

Anyway, First, if you have 4 people and use an average of 200L of hot water daily, 2 standard flat panels should give you about 50% of your hot water annually. The tank would be 300L (80gal). Anything above 2 panels and you reduce the effectiveness of the system unless you increase storage and/or shade a panel in the summer (or use a drainback system).

I would look into a large diameter (1.5" or so) corrugated stainless steel tubing in your big underground tank for domestic hot water and make it in a slinky in the DHW side of the tank. The volume could be big enough to hold most of the DHW draw of a shower and as it is flowing, it will take heat from the drainback tank. This system can also be made with pex tubing, maybe 4 runs in parallel.

A separate output of the tank could also go to providing heat for the HP.

Go for it.

PS...are you from Winnipeg?

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Old 01-26-13, 10:44 AM   #6
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Default Solar House...

I completely agree with randen, he's spent a lot of time researching & testing & building and it's working for him.

The chart you have there... I'm curious about it. Is it a chart of solar energy falling on a surface, or is it a chart of energy output from a particular solar collector? Also, I'm not sure that I understand what tilt angle the measuring device or solar collector is mounted at. The reason for my questions is that raw insolation values need to be de-rated for tilt and also for specific collector inefficiencies. So your thinking that went from insolation to area required for a particular amount of heat may be adversely affected.

Regarding the house part of your overall effort, here is a photo of the first Passive House:


Architectural beauty could be a topic for another discussion. But I have seen drawings of this house, and it incorporates quite a large number of great ideas that could be included in the house you have in mind.

Most notable is the large window exposure (large gain) on the side that will benefit from solar exposure. Also there is the small window area (small loss) on the other exposures.

Not visible form this photo is that the stairways from ground floor to upper floor are at the back of the house and have a separated air space from the front (solar side) of the house. I know that the stairway is not directly involved in fresh air or heat recovery. The only heat it gets is what might leak through the very thick wall. So it serves as a buffer for the back of the house, from the cold German winters.

On the bright side of the house, there is a vertical stack that goes from the ground up about 1/3 the height of the house. This is the air input for the house, and there is an underground run of ventilation pipe that warms incoming winter air, and cools incoming summer air BEFORE it gets to the Heat Recovery Ventilator.

Also not visible, is that Passive House building techniques incorporate a design that has very thick insulated walls, and arranges structural members in such a way that thermal flow through wood (R-1) is not continuous from inside the house to outside surface. They call this 'eliminating thermal bridges'. Almost none of the currently constructed houses use this technique. However it is required in several Scandinavian countries.

So, what all this house-talk means to you is this: If you can massively reduce your heating an cooling needs, then utilizing the fairly low intensity of solar energy & geothermal energy & water heat storage (compared to high energy density fossil fuels) your ideas regarding solar and heat pump optimization of your home will be well within your reach.

It's important to realize where we are in history. In particular in the history of petroleum energy development. We have benefited from, and adapted to an environment that is richer in cheap, dense energy than any era in the history of mankind.

We have become accustomed to this situation. Our transportation has adapted to it, our food production has adapted to it, our housing has adapted to it.

But just because we have become accustomed to it, does not mean it will continue.


Your project is really headed in the right direction.

Best,

-AC
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Old 01-27-13, 05:57 AM   #7
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Thanks for the all the feedback. A bit more about this house. It is not one I own, but right now is the leading contender for the property that I would like to buy. Currently it is a bit out of my prequal range, however the bank didn't try to qualify me for the maximum amount, only the amount I asked for. Cost wise for mortgage payment w/ taxes it works out to the same as the previous property I looked at because this house has dramatically lower taxes, so I believe I will qualify for it. Additionally there may be some wiggle room in the price because it has been on the market for 2+ years!

I will know in a week or two if I am getting it.

A bit more about this place. This house is about 3600 sq feet, so it is quite large. However it has a small 1 bedroom attached on one side, and a 2 bedroom apartment on the other side. The main unit I would guess is around 2100ish-2400 sq feet, much larger then I need, however I have a roommate that will rent a room, and possibly have another friend willing to rent another, so it the space won't be wasted.

Quote:
PS...are you from Winnipeg?
I am from Glens Falls, NY This home is about 10 miles from there.

As said in original post I do plan on tightly sealing the home first before pursuing the full scale of the solar system, but will design the initial system to be scale-able to replace all fossil fuel at the house. With any luck, a few years from now I will be installing PV on the roof as well, but I have much work to do before that.


Anyways, thanks all for the feedback, I wont have much to post for a bit till spring time when I'm moved into my new home (hopefully this one, who knows, maybe an even better place will turn up before I sign the dotted line). But I'll keep you guys posted here as things develop, and once I start these projects I'll carefully document all construction details and post my progress here.
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Old 01-28-13, 05:29 AM   #8
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I am from Glens Falls, NY This home is about 10 miles from there.

.
I ask because there is a Canadian football league team called the Blue Bombers....
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Old 01-28-13, 05:32 AM   #9
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ahh, the name is actually a reference to my trail hiking name.

My friends gave it to me after a particularly eventful summer in which I had some decent injuries (nothing real significant, but quite visible) in a short period.

They chose the name because in the game Super Bomberman (SNES) the blue NPC always seemed to blow himself up.
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Old 07-03-13, 12:26 PM   #10
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Finally have my clear to close for this coming tuesday for the house I mentioned above. Very much looking forward to moving in! What a headache this process has been lol =/

I have quite the large number of projects in mind, time and wallet willing hopefully. Look for project threads in the near future =)

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