Solar/Utility powered evap cooler

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System
System Posts: 2,511 admin
in Solar Beginners Corner #1
Hi all, this is my first post!

So I'm familiar with commercial utility power systems, but am a complete noob regarding solar systems. I have a general idea of the components, but am lost on specifics.

I'm trying to design a building with a solar/utility powered evap cooler integrated into the HVAC system. Is there a specific piece of equipment (a fancy inverter?) that can actively switch between the solar and incoming utility power to keep the evap running? I want the cooler to run on solar as long as there is sufficient power to do so, but switch to utility as needed.

Thanks folks!
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,448 admin
    #2
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    Re: Solar/Utility powered evap cooler

    The best solution (most efficient, least costly, least maintenance) are a set of Solar Panels plus a Grid Tied Inverter...

    Basically, the GT Inverter takes the energy from the solar panels and puts power into your home's wiring in parallel with the utility power. If your solar is producing more power than you use, then it actually turns your meter backwards. There are no switches or batteries involved and no maintenance (other than perhaps cleaning panels once in a while). From your home's point of view, there is no difference if you are using solar or utility power (other than your final energy bill).

    Currently, there is a 30% federal tax credit and perhaps some local rebates for you (check www.dsireusa.org for more information)

    This usually requires a professional installer, building permits, and utility approval.

    However, it is not cheap and not all electric utilities support Net Metered Grid Tied power systems.

    In the end, conservation is usually the first and best place to invest your hard earned monies.

    Insulation, double pane window, high SEER air conditioning, energy star appliances and lighting, etc...

    It is not that unusual for people to reduce their energy usage by upwards of 50% (if they never really looked at conservation before).

    I am not sure there is any good reason to add an evaporative cooler to an A/C system. The evaporative (swamp) cooler makes you cooler, in a dry climate, by adding moisture to the air. And A/C system makes you cooler by cooling the air itself and removing moisture from warm/humid air.

    They do make solar powered evaporative coolers. Here is one company (I don't know anything about them). However--I am not sure it would be a great investment for energy conservation unless you live in a true desert and have pretty high power rates.

    We have people here that are off grid (no utility power) and finding that the new Mini-Split A/C systems can be a nice solution for them. Very efficient and relatively low power. For smaller homes and/or cooling just a few rooms--but something that people have not done often before with off-grid homes. Larger A/C systems use quite a bit of power and take very expensive off-grid solar systems to power them.

    Our first suggestion is to do your research and planning before you spend any money on solar RE power... Yes it can make economic sense to install solar power, but there is a lot of planning/work before hand to make it work out well.

    Please feel free to ask questions... We were all in your place at one point or another in our lives and are here to help and educate.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • System2
    System2 Posts: 6,290 admin
    #3
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    Re: Solar/Utility powered evap cooler

    Thank you for the thorough and complete response!

    In my case, this installation is part of a "pre-cooling" system to reduce the ambient air temperature entering a 100% outside air AC system.

    The design isn't mine, I'm just hooking of the electrical. The HVAC guy had an idea to put the evap on solar when possible. A whole building solar/grid tie system isn't in the budget so I'm investigating this minimal approach.

    Do you know of a device that will switch back and forth as needed?
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  • solorone
    solorone Solar Expert Posts: 257 ✭✭✭
    #4
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    Re: Solar/Utility powered evap cooler

    Hi! Is this evaporating cooler the same as a swamp cooler, a fan with water? And what state do you live in?
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,448 admin
    #5
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    Re: Solar/Utility powered evap cooler

    What do you mean by a "pre-cooler"... There are water based cooling towers for A/C systems (pump, spray on coils, fan to move air through coils). (sorry, I looked for links/pictures of them--and all I could find were nuclear reactor cooling towers--same principle but a bit larger). The are pretty popular in other countries (like Taiwan) where power is a lot more expensive.

    If you are looking at mixing an evaporative cooler on the fresh air inlet for room air--I am not sure you come out ahead energy wise and you might run the risk of Legionnaires' disease by placing warm water in the wrong areas.

    The Grid Tied system is the answer to your question... Just about anything else will be more expensive and complex (assuming utility allows Net Metered GT systems).

    Otherwise, I am not sure I am understanding your needs (drawing air through a swamp cooler, pumping cooler water from a ground loop/well through a radiator, etc.)? And I am afraid to suggest anything as I don't want to get anyone hurt/ill over a half backed suggestion from me.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • AntronX
    AntronX Solar Expert Posts: 462 ✭✭
    #6
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    Re: Solar/Utility powered evap cooler
    Hairybroness wrote: »
    ...Is there a specific piece of equipment (a fancy inverter?) that can actively switch between the solar and incoming utility power to keep the evap running? I want the cooler to run on solar as long as there is sufficient power to do so, but switch to utility as needed.

    You can connect output from grid-tie inverter in parallel with input to evap. cooler. Then install enough solar panels to "displace" the grid power when sun is shining. This gives you seamless "switching" effect between solar power and grid power. No need for whole building solar, just as little as you want.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #7
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    Re: Solar/Utility powered evap cooler

    Bill's grid-tie suggestion is the right way to go here, in my opinion. It doesn't have to be a "whole building sized" system, just large enough to essentially off-set the energy usage of the pre-cooler. You might even see a bit of gain beyond that, as the panels will produce as long as the sun shines and the pre-cooler will cycle on and off. Granted it will run some of the night when the panels don't, but it will not run all day.

    Why make it more complicated than it has to be? :p

    BTW; if you think this will save money it is unlikely. Grid-tie energy production is expensive compared to most utility costs. Unless there is a good exchange rate on buy/sell and some financial incentives for the install it may not be worth the bother.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,448 admin
    #8
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    Re: Solar/Utility powered evap cooler

    I am sorry--I was talking about my HVAC skill levels--not yours or your installer.

    We try to be conservative here because we don't know what the other guy behind the keyboard knows or not--and we don't want to get anyone hurt or worse.

    Normally, if you have extremes between inside and outside air (winter or summer), a Heat Recovery Ventilator is usually the solution (basically used to temper the incoming air stream with the heat/cool of the exhausting air stream).

    Your building may already have this installed--it looks like a requirement for a few states and a country or so (Canada?).

    A few people here already have used them on their homes and are quite happy with them... I have thought about one for my home--but our temperatures are normally not that far from room temperature--so an open window usually is enough (my wife wants lots of fresh air).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,448 admin
    #9
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    Re: Solar/Utility powered evap cooler

    And, the Inverter/Switch + solar panels is already the GT Inverter. They are not too expensive (around $2,400 for a 3.3 kW unit). Solar panels are the more expensive part (nearing $10k for a 3.3 kW system). Add mounting, permits, wiring, etc...

    An entire turn key system will run (very approximately) $6-$8 per watt installed before 30% federal tax credits (business may get more credits/breaks).

    My two cents is that ~3kW of GT Solar is rough minimum to install... If you try to install less, the costs per watt may go up (although, with Enphase/etc. micro inverter--you can even install a 200 watt GT system if you wanted to).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • System2
    System2 Posts: 6,290 admin
    #10
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    Re: Solar/Utility powered evap cooler

    Thanks folks, I'll look at these suggestions!
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  • solorone
    solorone Solar Expert Posts: 257 ✭✭✭
    #11
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    Re: Solar/Utility powered evap cooler

    Well y'all about covered where I was slowly going, surely sounds inefficient and expensive for the possible return, I was curious as to the location of OP, as these type of systems vary in their own efficiency with the average humidity.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,448 admin
    #12
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    Re: Solar/Utility powered evap cooler

    I guess that HB is out of Phoenix Arizona area...

    Regarding Swamp coolers--from what I remember, even 40+ years ago, swamp coolers in Phoenix were being replaced with A/C units because of all the lawns/irrigation in the metro areas was raising the humidity of the outside air so much it was reducing the effectiveness of the evaporative cooler.

    If you look at the link for one company I supplied earlier, they give a chart about the most effective outdoor humidity for their operation vs exterior temperature (for example, if you want 72F cooled air temperature at 95F, the outside humidity needs to be 15% or less).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • solar_dave
    solar_dave Solar Expert Posts: 2,397 ✭✭✭✭
    #13
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    Re: Solar/Utility powered evap cooler

    I had a swamp cooler in Denver and when the dew point hits about 50 degrees they just stop working effectively. While they might be OK for early in the cooling season in Phoenix, the monsoon season destroys there ability to provide real comfort cooling.

    One interesting use might be to pre-cool the air headed for the AC condenser unit, rasing its ability to transfer heat. Comfort is not a concern there and any raising of effect heat transfer at the condenser might improve AC efficiency.

    I am sure someone here with more thermodynamics knowledge can weight in on this usage.
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