Asorption heat pumps?

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  • Telco
    Telco Solar Expert Posts: 201 ✭✭✭✭✭
    #32
    Re: Asorption heat pumps?

    Wow, lot of action since I was last able to get on.

    Sorry about the confusion, the link to radiant cooling was in response to a comment that it didn't work. From what I understand it's really only for arid areas, humid areas have condensation problems. I was planning on a fresh air system with positive humidity control so didn't see condensation as being a problem.

    My main goal was to find information on whether the absorption heat pumps were working and being sold yet. I guess as an alternative I could set up a chiller system that would bring water to near freezing, and pump it through a radiator inside the ventilation system or something, kinda like how an HVAC pumps freon through an evaporator to cool the air.
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  • russ
    russ Solar Expert Posts: 593 ✭✭
    #33
    Re: Asorption heat pumps?

    @Telco - you just described a 'fan coil' quite nicely. İn OK you probably have ground water temps in the low 60's - not much delta T for 'natural' cooling (meaning using direct ground water temp). What İ have is a air to water heat pump.

    @Bill - thanks for the comment on efficiency - in Germany a lot of study has been given to and proven the better ability of a flat plate collector to clear itself of snow.

    @icarus - the biggest problem with commercial solar thermal today is the very high cost for a rather simple item and that is slowing down acceptance - You are 100% correct that the flat plate can be cheaply built and function very nicely!
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  • LucMan
    LucMan Solar Expert Posts: 223 ✭✭✭
    #34
    Re: Asorption heat pumps?

    For solar thermal panel selection and capacities use this web site.

    http://www.solar-rating.org

    With the ratings you can determine the out put of the thermal panels for the different applications, IE pool heating, water heating, and air conditioning in different climates. With thermal panels capacities are all related to ambient air temperatures and the end water temperatures required.
    As stated before evacuated tubes will retain the snow for longer periods even when the sun is shinning because they are so well insulated, also the gaps between the tubes tend to hold the snow. Evacuated tubes also tend to frost over during below freezing weather. The differential controllers have a provision for circulating warm water through the collectors to melt of the frost
    I have a drain back system with flat plate panels and usually with in 2 hours after the sun shines they are free of snow and producing HW. Frost does not affect them as the sun melts the frost in a few minutes. Using a drainback system there are no worries about freezing because there is no water in the panels or connecting lines when the system is not producing HW all the water is stored in a tank in a lower conditioned area, no anti freeze required.
    The disadvantage of flat plates is that the max output HW temps are about 160 degrees F .
    U.S Federal and state tax credits help to reduce the final cost by 30 to 50% depending on the state that you live in.
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  • russ
    russ Solar Expert Posts: 593 ✭✭
    #35
    Re: Asorption heat pumps?

    The SRCC is a great tool and the basis of my qusetion for Bill earlier.

    İ prefer and would always suggest the pressurized system with an antifreeze solution on the panel side. Unless you have very soft water you don't really want the tap water constantly passing through the collector like some systems show.

    This morning İ turned off the electrical side of our system and with a solar 'direct normal radiation' of 3.62 kW/m2 our 305 liter hot water tank reached 60 degrees on top and 44 in the bottom section - the best for the past couple of months.

    As soon as it clouds up again İ'll turn on the power supply.

    İ still think the systems are grossly overpriced by suppliers - they are depending on the credits/incentives so that money goes into their pockets. To little savings to the consumer.
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  • LucMan
    LucMan Solar Expert Posts: 223 ✭✭✭
    #36
    Re: Asorption heat pumps?
    russ wrote: »
    The SRCC is a great tool and the basis of my qusetion for Bill earlier.

    İ prefer and would always suggest the pressurized system with an antifreeze solution on the panel side. Unless you have very soft water you don't really want the tap water constantly passing through the collector like some systems show.

    I agree about not running tap water through the panels.
    Drain back systems are closed loop to the panels with a heat exchanger either in the drain back tank or in the bottom of the water storage tank. Simple maintenance free, this system is a non pressurized, non glycol system utilizing gravity to return the heat transfer liquid back (water) to the storage tank. No danger of freezing, stagnation temps. or over pressure. No need to dump excess heat in summer, the controller has a high limit that turns the pump off and the system drains down, nothing left in the collectors or piping.
    Glycol systems require additional maintenance as the antifreeze solution should be replaced every 3 to 5 years because it loses it's anti corrosion properties and becomes acidic, high temperatures make it break down even faster, creating a gummed up mess. I have worked on too many glycol systems that were destroyed because of lack of maintenance.
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