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Old 12-07-10, 01:54 PM   #11
mrd
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I think this thread is missing some math! The title is how to calculate energy.. but I see no calculations.. At least, perhaps, some links to sites with calculations?

So many variables: latitude/longitude, local weather patterns, shading in the immediate vicinity, panel orientation, size, and type.

Type of fluid circulated, flow rate, any heat exchangers and their type/efficiency, storage volume(s) present, their dimensions/insulation and surrounding environment - or ultimate rate of heat loss, the desired output temperature/flow rate or heat rate..

There are many possible configurations. Seems the best we could do is to coagulate reference data and formulae for any of these possible components and configurations. I'd assume such a collection already exists somewhere on the web..

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Old 12-07-10, 02:10 PM   #12
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I am interested in seeing solar water(or other liquid) heating being made more versatile and applicable. Let's simplify the concepts and the systems to reduce the barriers to entry for parties interested in integrating such systems into hot water/space heating.

The panels and attached hardware up to a point constitute a system acting as a source of heat. This system is dependent on certain exterior factors to produce this heat, and it provides that heat to an attached exterior system. The rate of heat production is dependent not only on the exterior factors (location/weather/temperature) but also dependent on the internal state of the system.

That is, as the internal system heats up, it's efficiency of heat absorption is reduced. However, we would typically need a high temperature to transfer that heat into our destination, like a hot water storage tank.

A simple system could heat up a certain amount above our destination temperature, then we can induce circulation and allow heat transfer until we hit another lower temperature threshold. And allow this cycle to repeat. It's simple, but it's not efficient. We could optimize the efficiency if we minimize the temperature inside our heat source system!

A heat pump would be perfect for this, it could use refrigerant to efficiently transfer heat from our solar source to whatever our destination is. A path for hardcore do-it-yourselfers to follow to design and build their own heat pump to meet their needs would be sweet.

Although this is all speculation on my part. I'm unsure how much efficiency of transfer is affected with a rising solar panel temperature. Data would be necessary to determine if it's economically justifiable..
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Old 12-07-10, 02:13 PM   #13
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Also, integrating a heat pump would allow the storage of heat at a very low temperature to minimize heat loss and allow greater durations of storage...
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Old 12-11-10, 01:55 AM   #14
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I was not intending to arrive at a precise formula of how to calculate produced or anticipated energy. This was mainly about the fact that it is not straightforward to compare different heat sources like electric, combustion and solar.

As I mentioned earlier, the main problem with solar is to

1) Get a temperature which is high enough to meet demand (or lower the required temperature of the demand, to the solar temperature available)

2) Store solar heat either seasonal, weekly or daily


During all my research, thinking and experience so far, I have come to the conclusion that one of the vital points of solar heating (space heating in particular) is to maximize the difference between temperature available and temperature required.

To mitigate this challenge, it is vital to make a heat system with as large a surface as possible. Imagine if you could heat all floors in the house, and even all walls. In this case, even by the worst of winters, you just need to heat these floors and walls to 80 F or less. And the heat would be much more comfortable than a house with alternating cold windows, hot radiators and the resultant drafts and difference in radiated heat.

It is like a business and the bottom line. You can improve by increasing the sales, lowering the cost or a combination of the two.

To "increase the sales" is using a heat pump to transform the temperature available to a higher level, but there is a cost. This "cost" could be seen as "advertisement" in the business parallel.

To "reduce the cost" is in this case to lower the required temperature of the heating system. Although not exactly the same, the principle is the same. Because we use the simple method of combining two masses of heat (solar heating liquid, mixed with heating system liquid, in a heat exchanger). The temperatures of these two will merge, for the purpose of heating the house. But without a heat pump, there can be no heat transfer unless the produced temperature is higher than the required one.

To have a lower required temperature of a space heating system with a large surface not only increases the efficiency and extent to which you can extract heat from the solar panel. It also means that storing heat can be done at a lower temperature. The lower the difference between the heat storage, and the surrounding temperature, the less the loss.

In my system, the seasonal heat storage is high volume, low temperature, placed below the house. Insulated on the sides, the top is the house, and the bottom will eventually saturate over the years until it stabilizes somewhat. (providing ground water is not too close to the ground).

Whatever heat loss is upwards, goes into the floor of the ground floor. And whatever heat loss there are to the other sides, is not really that great a loss. Remember, this heat is excess summer heat, which is close to free and could not otherwise have been used. The energy it takes to pump it into, and out of the ground, is so minor it is easily made up by photo-voltaics.

As the final backup, one can add on a heat pump to make hot water for taps and shower out of the heat storage temparature, and to get the last bit out of the heat storage in late winter and early spring. Since the heat increase here is quite minor, this heat pump would run at a quite high CoP, especially compared to a heat pump trying to make hot water out of freezing air!

As for the calculation of how much heat is actually produced it is quite easy. All it requires is one flow meter, two temperature probes and a meter. The meter needs to be calibrated for the liquid used, like in the case where glycol or other anti-freeze liquid is used. If the meter has a logging function, one can compare the heat produces against other factors, like outside air temperature, available sun, time of year and so on.

I will take measurements in my system at the relevant places, and log these data for later analysis, to prove how much heat it is possible for me to extract and store from this system. And I will hold future energy bills toward historic ones, and compare energy production and usage from before and after the installation of this system. As electricity and heating rates increase over the year, I will keep producing my own heat, and the same close-to-nothing rate. All I need to pay is interest on loans, and minor occasional maintenance.

Finally, I will sum up all the expenses, and all the savings, and I will include all the added benefits as "savings". It would not be fair to expect the energy bill savings to entirely sponsor all the improvements done to the house while doing this project.
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Last edited by osolemio; 12-11-10 at 02:05 AM..
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Old 10-15-11, 02:47 AM   #15
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Default Missing posting?

Michaelgale40 posted this text below, according to an email notification I got - has it been deleted?

Quote:
Thanks you for giving me such great information.Appreciate your page, good reading, thanks
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Installing all this in a 30 year old house, Copenhagen, Denmark. Living in Hong Kong.
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Old 10-15-11, 03:02 AM   #16
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Default Delays, delays

I am still here, and I am still working on my project.

The solar panels are just about ready from the factory (finally) but as winter is approaching, I will have to wait for the spring. To remove the tiles from the roof, I need warmer weather, as the tile glue is solid below 60F or so. On a normal sunny day, the tiles can be removed easily without too much effort.

I am working on the garden (hard surface, the garden is so small, there is no lawn!). The seasonal insulation in the ground is all done, just a few cosmetic touches to go, yet the control system inside the house is not assembled (no point yet, as there are no solar panels yet)


Rainwater system is up and running, and has been for a while. The tank is 7500 liters, which is roughly 2000 USG. At the moment it supplies water for toilet flushing, washing machine, cleaning purposes and so on.


I am in the process of investigating the possibilities of making a legal installation where rain water is also used for hot water and most of the remaining cold water in the house. We would retain a number of dedicated taps (cold water only) for drinking and cooking.

The filters in question would be three stage: particle, active carbon and finally UVA filter. Probably in dual, with monitoring, to ensure quality and supply (auto shut down if a UVA lamp fails, and then the other system keeps working).

Financing is a problem too, paying as I go out of the paycheck - with what remains after the worlds highest marginal tax rate has been applied. Delaying the solar panel installation until spring gives me time to breathe (make more money) for the final but crucial investments.

I look forward to be able to present data here, to document what I meant when I started this thread.

It will be accompanied with graphic presentations to illustrate the function of the system - any suggestions to what programs (Mac!) to use? I prefer something which is not too complicated, and if it can make web enabled presentations, that would be preferred (no flash, please, or other proprietary or complicated formats. Html5 format preferred!)
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Old 10-15-11, 09:10 AM   #17
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Quote:
Originally Posted by osolemio View Post
Michaelgale40 posted this text below, according to an email notification I got - has it been deleted?
Yeah, he was a spammer.
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Old 12-03-11, 06:48 PM   #18
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Great info, I will be looking forward to this thread as things move along. Please post pics.
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Old 12-04-11, 10:20 AM   #19
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Default Heating with the sun

osolemio

We have been pursuing solar hot water heating for a couple years now. It has been quiet successful. There are 160 sq ft of flat plate collectors mounted to the wall of the house and have been in operation for two years. With good sun on them we heat for a 24 hr period via in floor heat. Back-up heating is via ground source heat pump. This weekend we have installed the last panel for the house. It is an additional 88 sq.ft. that can be adjusted for the seasons.
Your system sound great. Keep forging ahead. Solar heating works well. Who ever thought you can heat a house with the sun.? Here in Canada there is a comunity with an installation such as yours. The comunity uses bore holes in the earth to store massive amounts of heat. Check out Drake Landing (dlsc.ca).

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Old 02-05-12, 10:09 AM   #20
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I currently have a ground source heat pump in my house and am looking for ways to incorporate solar heat. I prefer a large tank and low temperature. I have considered a large water tank and floor heating. Another option I have not seen suggested is to use a large tank to pre-heat water going into my heat pump. I have an open loop system that uses water at about 53 degrees. If I can heat it to 70, or even 60 degrees, it will increase the efficiency of my heat pump. It would be even more effective on closed loop systems because the ground temperature decrease as heat is removed during the winter.

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