Batch system solar hot water heater converts to air-conditioner

    Batch system solar hot water heater converts to air conditioner. I live in a climate which experiences freezing temperatures but still for much of the year hot water can be supplied by a roof mounted batch heater. Since these systems are drained into a storage tank at night there is no need for anti-freeze or any sort of electronic controls, thermostats, heat exchangers, circulating pumps or other expensive to buy and set up maintenance creating headaches. You simply fill the unit in the morning, shut off the water once it's full and drain into your large storage tank in the late afternoon. No bells and whistles to break down. A float valve just like inside your toilet tank prevents overfilling. The system is not pressurized. Many breadbox style heaters work this way.

    Now the air-conditioner part. This only works in climates which experience cool evenings after the heat of the day is over. I used to live where summer nights were so hot it felt like I was going to rot and this unit would not work in that sort of hellish environment. Since the batch heater is drained down in the late afternoon it is now available to cool water overnight. During the day this water would be stored in a large tank which is suspended from the ceiling just beneath the collector. A simple pond pump would send water from this tank up to the collector at dusk each day and the water would be drained back into the tank early in the morning when the collector reaches its coldest point. Since the tank is up high , the air which it cools will flow towards the floor and no fan will be required. The tank will condense water on its surface and this water needs to be collected. A simple curtain would insulate the tank since it's cooling capacity is greatest in the early morning but will not be needed until the afternoon when the house warms up.

      In areas where evening temperatures are not low enough for this to work well you could still use a system similar to this if the temperature of your well water is sufficiently low. Each afternoon the air conditioning tank could be filled with cold well water. This water would absorb heat from the room and this  warm water could be pumped into the batch heater in the morning. This preheated well water would now sit in the sun all day to provide your hot water. You get air conditioning and a more efficient batch heater

For more aggressive passive cooling ideas for hot climates, start at this wikipedia article. It explains solar chimneys and passive down-draft cooling towers. There is a lot traditional vernacular architecture in the Middle East, Africa and South Asia that utilize systems like those described. There are some modernized designs done in Israel that could be adapted to the Great Basin, Colorado Plateau and Mojave and Sonoran deserts. It has been many years since I read about them (I found them by checking the card catalog and browsing the shelves in the library -- what we codgers did for casual learning before the internet and Google). I will look around the internet for some newer references.

Also, there a a few active solar cooling designers and manufacturers. I have been monitoring the progress of Solarfrost, located in Austria, for a few years. I was told once that there is a manufacturer of a similar system in Arizona or California, but I was not able to track it down. The nice thing about them is that they can utilize a solar heating system sized heat a house in a cold winter and use the normally little used Summer sun to cool the house, and other things. Not cheap, though.

I should have mentioned that the water used for this sort of air conditioning will build up legionella bacteria and should not be used for bathing or drinking when a system is bled down. Also, this would need to be a separate system from any that produces hot water but it is basically the same components run during different hours of the day.

I have used a container of water set on the roof of my vehicle to cool over night to keep food fresh in a Coleman cooler. I then fill that same container and put it back on the roof where it heats in the sun, providing a hot or warm bath depending on conditions. To view photos of this primitive but effective method, click here. Heating Water With My Van - Solar and Waste engine heat. https://permies.com/t/18290/solar/Heating-Water-Van-Solar-Waste

Dale, is your idea anything like this video?

http://www.youtube.com/watch?v=UXGlB1kGO5E

Basically he takes some pipe in a spiral and secures it in place with 2 boards in a cross and lays it on a tin roof.

Seems like this could be used for more than just showers too, like heating a green house.

George Meljon wrote:Dale, is your idea anything like this video?

http://www.youtube.com/watch?v=UXGlB1kGO5E

Basically he takes some pipe in a spiral and secures it in place with 2 boards in a cross and lays it on a tin roof.

Seems like this could be used for more than just showers too, like heating a green house.

No, nothing like that. That system would be difficult to drain down at night and it would be easy to achieve scalding temperatures on a hot day. A simplified bread box heater is easy to drain down.

http://www.youtube.com/watch?v=tqUwBwfN5iE
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This thread contains more recent thoughts on the matter. https://permies.com/t/30830/solar/Dale-Super-Simple-Sizling-Solar