Solar air conditioning

mcgivor

One of my future projects is to install air conditioning to at least the room where I sleep, 35 deg. C at night is less than comfortable. Mini split inverter units are widely available with SEER ratings of 27, but during my search I stumbled across solar assisted AC, has anyone any knowledge or experience with this, seems intriguing especially when off grid. To save time explaining, ive included a link and PDF.
http://www.saveenergyasia.com/solar-air-conditioning/

dennis461

Some sceptics writing here..
http://hvac-talk.com/vbb/showthread.php?1385401-Solar-refrigerant-panels

And it may not work at night without the sun

Photowhit

There is another "solar" air conditioner, that uses solar photovoltaics to run the outdoor unit uses @1000 watts of solar panels. I think it's been discuss or at least brought up here. I asked them some questions about over paneling and their suggesting it couldn't run "off grid", wanting to run the additional current off my main system. They never responded. I'll hunt it up later today.

solar_dave

mcgivor said:

One of my future projects is to install air conditioning to at least the room where I sleep, 35 deg. C at night is less than comfortable. Mini split inverter units are widely available with SEER ratings of 27, but during my search I stumbled across solar assisted AC, has anyone any knowledge or experience with this, seems intriguing especially when off grid. To save time explaining, ive included a link and PDF.
http://www.saveenergyasia.com/solar-air-conditioning/

Your 35C at night is the key. Any solar support would be non existent at night.  The best way to get solar AC is to grid tie and spin the heck out the meter in the good direction.  We went from $6500 annual electric bill to about $600 annually by grid tie and net metering, BTW we increased loads during that period (see below).  Ours too has the limitation that night time usage doesn't get support from daytime solar, part of the TOU plan is that generation credit can only go against the TOU that it was generated, but electric at about $0.025 a Kwh for night-time generation (without delivery charges) almost makes it hardly even worth watching.

We have a 20 seer 3 ton mini-split on our workshop/office and by taking normal conservation efforts our peak consumption was in July with 640 kWh worth about $75.  Expensive without the grid tie payback.  Add that to a pair of 3 ton Tranes doing the main house, a swimming pool pump to run and a pair of electric cars you can see that $600 annual electric is pretty darn good with a rapid ROI.  

Caveat to all this, the cheapest way to solar nirvana is first to conserve.  It gets repeated a lot around here that a watt saved is way cheaper that a watt generated.

Dave Angelini

I have been wondering Dave what the modern (now)  equivalent is to the old rule " It gets repeated a lot around here that a watt saved is way cheaper that a watt generated." it use to be 3$ on solar for every 1$ on conservation.

Mcgivor  The above thread is for grid tie and does not apply really to you. I must get 2 or 3 e-mails a month from salesman telling me they have a new way to cool with solar.  My mini-split has been cooling my offgrid home since 2007 flawlessly. I have added a second as a back-up and a 9Kbtu to 12Kbtu is all I have used for dozens of folks offgrid. There is a link here to some of the things that are required.

http://forum.solar-electric.com/discussion/23007/mini-split-update-for-offgrid#latest

bill von novak

mcgivor said:

One of my future projects is to install air conditioning to at least the room where I sleep, 35 deg. C at night is less than comfortable. Mini split inverter units are widely available with SEER ratings of 27, but during my search I stumbled across solar assisted AC, has anyone any knowledge or experience with this, seems intriguing especially when off grid.

1) Doesn't make sense.  Heating refrigerant works with an absorption-cycle refrigeration system, not a compressor based one.
2) Even if they redesign the thing so it's an absorption refrigeration system - it won't work at night.

If you want to reduce the cost to run A/C, then solar grid tie systems are proven and cheap.

Photowhit

Perhaps we should have this discussion in Off grid, I have an off grid system, in my location it wasn't reasonable, with 1/2 the solar system paid for, to do a grid tied system in an area where grid tie was not welcomed. My local cost to have the opportunity to buy electric is now $32.50 per month and will go up shortly. When I was looking into doing a grid tied system, there was only net metering for the month involved and no rollover (that has not changed) and they wanted you to have 2 meters, one buying and one selling and they wanted the user fee for both (this has changed to a single meter/charge, but I believe they still want you to pay for the meters calibration annually). The user fee is paid monthly and is NOT part of the net metering. There are reasons to be off grid, even within the lower 48.

McGivor, for what it's worth, a window unit is not a huge problem to run. You don't have your system in your signature, I tried to update mine 18 months ago and it wasn't simple, but worth the effort in reviewing what you have and possibilities.

I've run a window unit in a well insulated cabin, done right. on a very minimal system. 4 Golf cart batteries, 24 v 1800 watt inverter and originally 1000 watt array, expanded to @1500 watts. It provided about 6 hours run time enough to sleep in original configuration and once expanded, I was able to run during the day time once the charge controller was out of bulk. In Missouri our heat comes with sun, so mostly worked fine, batteries lasted 5 years 4 of which they ran an A/C. They minimal extras during this time, a small fridge, though I even shut that down the first 2 summers to have more A/C time. I lived a mile from work and used the fridge there.

BB.

You can create/edit your signature here:

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-Bill

westbranch

Mcgivor,  some  years back we traveled around Thailand and Fiji in Feb.  The most comfortable sleep I can remember was under a ceiling fan on slow, it got so  cold we located a second sheet to keep our  bodies 'warm', it really was cold when the sweat starts to evaporate off the skin......
I hate the sounds of an in-room AC, generators charging my battery, and logging truck JAKE brakes at 2AM in the winter and summer...
so alternatively build your self a COLD (bed)room and insulate it, then cool it in the day with a mini split and have a ceiling fan for times when it does not stay cold enough.... ??

Mangas

And, even the central A/C variable speed compressors and handlers are now amazingly efficient.  As posted earlier, I figure we reduced our off grid power consumption by over 25% by moving to these ultra high efficiency A/C units. Sunrise bank voltages proved it.

I was tentative but glad my HVAC contractor talked me into it despite my old HVAC units being 11 years old. Scrounge conservation, capacity and build storage in place wherever we can find it!

I am sure the minisplits will enjoy the same engineering evolution over time. I've heard they're dependable and very cost effective. I may install one in a small adjacent stone building.

mcgivor

bill von novak said:

mcgivor said:

One of my future projects is to install air conditioning to at least the room where I sleep, 35 deg. C at night is less than comfortable. Mini split inverter units are widely available with SEER ratings of 27, but during my search I stumbled across solar assisted AC, has anyone any knowledge or experience with this, seems intriguing especially when off grid.

1) Doesn't make sense.  Heating refrigerant works with an absorption-cycle refrigeration system, not a compressor based one.
2) Even if they redesign the thing so it's an absorption refrigeration system - it won't work at night.

If you want to reduce the cost to run A/C, then solar grid tie systems are proven and cheap.

It appears that it is an add on to the AC unit, superheating the refrigerant before the compressor thereby aiding the compressor by relieving it of some of the energy required to compress (heat) the gas during the day. In essence it would be a hybrid absorbtion/compressor setup which at night would work as a regular AC unit.
  
My guess is that modifying a new AC unit would void any warranty unless you purchase one of their manufactured units which includes the solar add on , my plan is to use a mini split high SEER rated unit during the day to remove the latent heat in the concrete floor and walls, using excess PV output  , so by the end of the day the AC would have a head start, so to speak . The room is on the north east corner and despite using lightweight cellular block, ceramic paint, ceiling  insulation and shading with banana trees it's a loosing battle with 47C day time temperatures, without some form of cooling.

The grid is about 800 meters away and the feed in tariff is good, $ 0.12 US. per Kwh but to make the cost viable to connect would involve investing in more array capacity >25 Kw, which has been under consideration, the space is available flat and un shaded, so before proceeding with enlargement of off grid I should consider spending $100 000.  

Another thought was, if this works, why have the likes of Diakin, LG, Samsung, Panasonic etc not used it, or is it just another wonder gimmick to liberate you of your hard earned money.

Photowhit

Nice tariff! Wonder how long they would guaranty that? That's above the wholesale price? I guess it would mean setting 10-12 power poles...

mcgivor

Photowhit said:

Nice tariff! Wonder how long they would guaranty that? That's above the wholesale price? I guess it would mean setting 10-12 power poles...

Gaurentee is 25 years, used to be $0.15 but was lowered due to panel prices dropping. The rate for residential is $0.14 currently, the government who owns the grid purchased at a net loss, in the past, to promote the expansion of private solar farms, the rational being that the fossil fuels used in the generation of much of the nation's needs was subject to market price fluctuating, usually in an upward trend.

westbranch

McGivor, we have been in both Thailand and Fiji in February, and the most comfortable sleep I can remember was under a plain old ceiling fan... some places even had desk fans , but the ceiling fan on slow made you cold enough to go and get another sheet so your body temp did not drop.
Alternatively build  yourself a COLD Room and use a mini split to cool it down... what about a hydronic tube system, used for cooling rather than heating, in that concrete floor?  You would want some insulation under the concrete though..http://www.beaverplastics.com/Insulation/documents/insulworks.pdf

mcgivor

The temperature depends on where and when you are, April and May are the hottest here, 560Km NEof Bangkok 300m above sea level , right now the weather is perfect, 28C max 18C min, but when it's 47C and 35C, it takes a few weeks to heat everything up, inside it can remain 40C all night, usually sleep outside during those months. Near the coast the water moderates the temperature, same as the difference between Prince Rupert and Ft. Nelson. The house is already built, so the cold room, mini split is the answer, the heat punishes everything, battery, output and demand, we all have our challenges  

Dave Angelini

Micro-climates are most everywhere. Anyone who has spent time in the tropics knows that the other side of the hill can be vastly different in comfort when sleeping at night and can vary from week to week.

 We spent quite a bit of time anchored off land places that needed cooling at night. Some did not and were quite comfortable.
I remember leaving the boat closed up for a trip inland for a week. When we came back, anything that was leather had a coat of mold on it.

I won't even go into how uncomfortable it can be cooking a meal when it is that hot. What about the challenge of Happy Hour?
The one thing you will love about the mini-split is how quiet it is indoors and outdoors. I can't imagine listening to a window unit.

westbranch

Yes, Up around Udon Thani can be sweltering hot and wet... prefer it to Bangkok though. 

Wife escorted Nursing students from here several times on an exchange study to that ''small isolated village'' as their travel guides referred to it... What an understatement!

bill von novak

mcgivor said:

It appears that it is an add on to the AC unit, superheating the refrigerant before the compressor thereby aiding the compressor by relieving it of some of the energy required to compress (heat) the gas during the day. In essence it would be a hybrid absorbtion/compressor setup which at night would work as a regular AC unit.

??? That makes no sense.  Increasing the temperature of the refrigerant makes the compressor work harder (has to compress to a higher pressure to get the extra heat out of the system.)

And how is it an absorption refrigerator?  Where is the absorber fluid?

I have a feeling someone read the term "superheat" and thought "that means I should heat the refrigerant!"

mcgivor

bill von novak said:

mcgivor said:

It appears that it is an add on to the AC unit, superheating the refrigerant before the compressor thereby aiding the compressor by relieving it of some of the energy required to compress (heat) the gas during the day. In essence it would be a hybrid absorbtion/compressor setup which at night would work as a regular AC unit.

??? That makes no sense.  Increasing the temperature of the refrigerant makes the compressor work harder (has to compress to a higher pressure to get the extra heat out of the system.)

And how is it an absorption refrigerator?  Where is the absorber fluid?

I have a feeling someone read the term "superheat" and thought "that means I should heat the refrigerant!"

Not being a refrigeration expert, l'm having trouble understanding the concept of the theroy myself, was wondering if anyone knew about, or had any experience with regards to the concept. The question would probably be best asked in a refrigeration forum, rather than here, where the focus is primarily of an electrical nature.

mcgivor

westbranch said:

Yes, Up around Udon Thani can be sweltering hot and wet... prefer it to Bangkok though. 

Wife escorted Nursing students from here several times on an exchange study to that ''small isolated village'' as their travel guides referred to it... What an understatement!

I'm located about 19Km due east of Udon Thani, yes Bangkok is more humid which makes the heat uncomfortable, when it's hot here, usually it's dry, the rains lower the temperature to 35/28C but humidity rises, but having spent most of my life in the tropics, it is where I prefer to be. Spent the last 20 years in Vancouver, the cold and wet got me down, actually preferred the cold and dry of the north, minus 20C is somehow warmer than 1C with rain,

Dave Angelini

You are going to have to learn some refrigeration to hook up the split as it sounds like you are not in a place that has refrigeration techs.
I have walked my clients through it but they had to buy a vacuum pump, line set, and a valve adapter.

mcgivor

Dave Angelini said:

You are going to have to learn some refrigeration to hook up the split as it sounds like you are not in a place that has refrigeration techs.
I have walked my clients through it but they had to buy a vacuum pump, line set, and a valve adapter.

All the dealears, there are many, include installation in the price,  the ones I am considering are Diakin and Panasonic variable output  8-12 K BTU inverter, both are $630, Panasonic is 27 SEER vs 24 Diakin

Dave Angelini

Nice !  I wish it was that way here. Many, and I mean many have had to roll the dice with warranty and install their own here offgrid.
The good news is the inverter based splits have a 5 year warranty and are definitely up to the task.