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Solar Cooling: The Next Frontier for Distributed Generation?

By Badal Shah
December 31, 2012   |   17 Comments

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The information and views expressed in this blog post are solely those of the author and not necessarily those of RenewableEnergyWorld.com or the companies that advertise on this Web site and other publications. This blog was posted directly by the author and was not reviewed for accuracy, spelling or grammar.

17 Reader Comments
Comment
1 of 17
December 31, 2012
Excellent article. Commercial-scale solar thermal cooling systems are the need of the hour. West spends more on heating while East spends more on cooling. IT and other industrial establishments use enormous power for cooling besides domestic Air-conditioners. With frequent power cuts in developing countries like India, solar cooling will be the answer. Will Chinese Solar Manufacturers look come out with an affordable Solar Air conditioners for wider use in developing countries. Different methods employed in solar cooling:Air can be passed over common, solid desiccants (like silica gel or zeolite) to draw moisture from the air to allow an efficient evaporative cooling cycle. The desiccant is then regenerated by using solar thermal energy to dehumidfy, in a cost-effective, low-energy-consumption, continuously repeating cycle. A photovoltaic system can power a low-energy air circulation fan, and a motor to slowly rotate a large disk filled with desiccant.
Energy recovery ventilation systems provide a controlled way of ventilating a home while minimizing energy loss. Air is passed through an "enthalpy wheel" (often using silica gel) to reduce the cost of heating ventilated air in the winter by transferring heat from the warm inside air being exhausted to the fresh (but cold) supply air. In the summer, the inside air cools the warmer incoming supply air to reduce ventilation cooling costs. This low-energy fan-and-motor ventilation system can be cost-effectively powered by photovoltaics, with enhanced natural convection exhaust up a solar chimney - the downward incoming air flow would be forced convection (advection).
A desiccant like calcium chloride can be mixed with water to create an attractive recirculating waterfall, that dehumidifies a room using solar thermal energy to regenerate the liquid, and a PV-powered low-rate water pump.
Dr.A.Jagadeesh Nellore(AP),India
E-mail: anumakonda.jagadeesh@gmail.com
Comment
2 of 17
January 2, 2013
To Anumakonda, Once a dessicant is 'mixed' or filled with water or moisture, its dehumidification effectiveness is null. Please clarify the meaning of your last paragraph,

MannyHM
Comment
3 of 17
January 2, 2013
@Dr JAgadeesh, Dessicant cooling is feasible if you have two or more applications operating in tandem. For example, the room cooling operation + vegetables/fruits/cash crops cooling operation complimenting each other. In the end, you will still require a cooling tower which use water as cooling medium, but a lower rated capacity. Pl. note CaCl2 has limitation for cooling i.e. cannot cool below 20 deg C. So at 20 deg C., what cooling you would like to propose on Industrial Scale? Please enlighten us.
Comment
4 of 17
January 2, 2013
Mr. Shah's article brings promising news regarding solar AC for the commercial and industrial sectors. Here, concentrating solar and multi-effect absorption chillers are an efficient combination but are capital intensive retrofits for buildings at any scale. I wonder how their economics compare with currently-priced fixed PV retrofits, even though these systems are not up to handling HVAC loads but rather oriented towards offsetting peak loads in grid-feed situations. At residential and small commercial scales, the availability of small dual-effect chillers is a problem to be solved. Currently, these are complex, expensive systems that make sense at larger scales. Traditional vapor-compression AC is plug-and-play and not so capital intensive. Still, there's a huge solar potential to be tapped given the right technology and financing. I've been advocating a concentrating roof solution to reduce capital expenditure on the solar collection part of the equation by sharing structural costs between building and solar components. On a more general note, let's hope interest and awareness in solar AC continues growing in 2013!
Comment
5 of 17
January 2, 2013
If I remember right, solar dessicants are effective but increases the salinity in the air and will increase corrosion related wear on metal in it's vicinity.
Comment
6 of 17
January 2, 2013
This article fails to provide any substance on what technology is being used and what the economics of the technology are.

I have been following solar cooling systems since I attended a presentation by 'Solid Energy' (http://www.solidsolar.com/id4.html) at Solar Power 2006 (now called Solar Power International). At that time, Solid claimed to be on the cusp of major developments for solar AC using ammonia absorption chillers. Their flagship project then was (and still is) just north of Phoenix, but it has proved to be economically unviable. According to my very credible sources, the Solid system is very complex and maintenance intensive.

While Bangalore probably has higher electricity rates than Phoenix making the economics more favorable, this article fails to provide any substance on system configuration. A quick check of the manufacturer website shows they do not specialize in anything in particular. They appear to offer everything solar from utility scale PV installations, to home cookers, to LED lighting solutions.

The technology mentioned in the article above appears to be similar to Solid, so I do not see this as anything new without hear more about the technology that makes it different than Solid.

Without more detail I am assuming this is just another effort to secure investor dollars without divulging specifics on the technology. I understand this article being posted on REW, but I cannot understand how a technology with so little vetting is able to make the email notifications.
Comment
7 of 17
January 2, 2013
Solar thermally driven 2E absorption chiller cooling and heating systems are cost-effective for systems of 100 tons and higher when federal and state solar incentives are included. Such absorption chillers require solar temperatures around 350F, and suitable tracking and non-tracking solar collectors are now available that will consistently achieve this performance. The preferred backup fuel is natural gas, and its current low price adds to the cost-benefit for this system. A solar 2E absorption cooling and low pressure steam plant has been operational at the Steinway and Sons manufacturing plant in New York City for about 2 years, and I can be contacted at thenkel1@nc.rr.com for more information about this project.
Comment
8 of 17
January 2, 2013
As with most solar thermal applications cost effectiveness comes with the combination of low cost unglazed solar collectors like the Powerstrips my company, Hot Sun Industries Inc manufactures, in combination with low temperature loads. Simplicity is the answer to cost effective solar without government incentives. Including incentives in the payback number doesn't allow us to evaluate the technology on its merits relative to fuel. Huge storage underground and huge banks of low cost unglazed solar collectors operate at night cooling the tank. There's your cost effective solar cooling technology. Not very sexy, not very high tech, and not very marketable but if quick payback, competitive with fuel, and straightforward is what you want we just have to accept this new approach to solar thermal. We're doing municipal projects in Canada right now where we're adding heat to ground sources and doubling COPs of heat pumps by heating fluids that are cold even in winter. Unglazed plastic pool heating solar collectors are the low hanging fruit of the solar energy field and they are largely uncounted and ignored because those of us in this field are simply busy implementing it in applications like residential pool heating instead of trying to crack new markets in competition for subsidies with the plethora of clean tech high tech devices we all prefer to believe will save the day. The solar solutions of the future are low tech and right in front of us.
Comment
9 of 17
January 2, 2013
Joel Fairstein

I'm trying to envision you concentrated solar roof and its shared structural component. Do you not need moving components to follow the sun with CSP?
Have a look at this solution www.orionsolartech.com
It is a building integrated, photovoltaic, thermal, structural panel that makes the roof and is also good for rain water collection.
Read the OVRVIEW and look at the 17 drawings under the DETAILS tab to get a good understanding.
I think it is the most versatile and dynamic system there is and will allow Architects and Engineers an unprecedented ability to apply solar to their projects.
Comment
10 of 17
January 2, 2013
David Coles
What temperatures are needed for you solar cooling system and would it be compatable with my PV/Thermal system mentioned above?
I have this vision of a complete solar contained heating and cooling electrical system that fuels the family car. Is that too much to ask for?
Comment
11 of 17
January 2, 2013
Gary, my design uses a mirrored roof forming a shallow, non-imaging curvature. A linear evac tube array above it tracks focus as solar declination changes. The resulting high fluid temps allow driving of dual-effect chillers. Except for pumps, there are only five moving parts. It's not a retrofit though, an advantage of the system Tom Henkel describes above. (I'd love one day to walk the Steinway roof and then explore the pianos below it!) Regarding your system, Gary, a look at your figure 5 drawing tells me you've embedded water pipes and storage into the PV roof panels to capture heat. Why water and not glycol pumped into heat exchangers, especially for Canadian winters? Otherwise, it's an interesting setup. Let's hope it it can pass heat cycling tests and maintain roof seal. Also, how cost-effective is it compared to a standard PV installation with Chinese pricing? (I'm sure Siemens had asked themselves the same question when they announced closing of their CSP operations).
No image available
Comment
12 of 17
Anonymous
January 3, 2013
I'm a mother of a 17 year old boy in Spain who has to build a PV panel as a school project for IB baccalaureate. I have been following the developments of PV for some years but with the rapid changes in technology feel lost at to which would be the most energy efficient latest technology, yet economically viable as a home project and therefore would need your direction and guidance to do this successfully. With the rapid ever increasing exorbitant costs of electricity in Spain, I want to get involved in doing this as a family project with my three kids and at the same time help my son to do a great job. In this way I might entice them to get passionate about sustainable, renewables energy and self sufficiency.
Many thanks in advance
Astrid
Comment
13 of 17
January 3, 2013
Check out the Swedish company Climate Well, (www.climatewell.com)they have a solar AC system which seems to be very capable. I'm waiting for its introduction in the US.
Goran
Comment
14 of 17
January 3, 2013
My instincts tell me that more complicated solar heating systems are unlikely to beat simpler PV systems in the long run for most AC applications. Grid tie PV with a high efficiency AC unit is much less expensive over the long run compared to ammonia chillers or any other technology I have seen. Solar thermal works well for water heating, but solar PV is starting to become a viable cost alternative for even domestic water heating for many people.

Using unglazed collectors for solar cooling would have little impact on the really hot climates and would be practical only in areas where night temps are low enough to provide real cooling. The lows at night in AZ are often over 90 degrees making unglazed poly tube systems impractical. The same is true for much of the country where AC is a major load. These systems make work ok in cooler markets, but I have doubts to the cost effectiveness of this approach for most areas.
Comment
15 of 17
January 3, 2013
A solar-driven 2E absorption chiller cooling and heating system with natural gas backup permanently relieves the grid of electric power demand, roughly 1MW for every 1000 tons of cooling. PV-driven vapor compression cooling will always require electric power backup from the grid. Therefore, using PV for cooling will require energy storage of some type in order to accomplish the same grid power demand reduction. Gas fired 2E absorption chillers are very popular in the NYC region and other areas with high electricity rates, and the life cycle costs for these chillers are less than for vapor compression chillers, especially now with low natural gas prices.
Comment
16 of 17
January 3, 2013
Highest outdoor temperature can be up to 95 degrees F and can be cooled down to as low as 65 degrees F with humidity levels as low as 50% depending on the location of the unit. Our system can be used with PV systems but at a higher cost for transitioning the power. Our system can also provide heating as needed simply by reversing certain operating stages in the cycle. We guarantee a maximum of 70% in energy cost savings utilizing our Solar HVAC System. We also provide a safety net HVAC System to combat any Chemical Warfare attack against an HVAC system. See our blog: http://wp.me/p2n9x2-9 and visit our web site at www.dcasystems.com for an introduction to our latest R & D efforts.
Comment
17 of 17
January 15, 2013
I am very surprised that the companies involved have not thought about the very lucrative ways they could provide cooling opportunities to certain key businesses that already expend large quantities of power to heating systems and cooling systems at the same location, making solar thermal cooling the perfect solution for their problems of keeping dining areas cool for customers, but allowing the heat of their ovens for Pizza, or Glass blowing/Kilns businesses, to be as hot as it needs to be, and separating them by super-non-conducting heat shields, could allow both functions to work effortlessly and be a true benefit for the costs of cooling or heating, depending on which is best for which part of their buildings. The savings would not just be for the businesses then, but for all the other businesses that share energy sources and must be subject to reduced capability as a result of not having it. It just makes perfect sense to reduce costs and reduce demand on the energy trunks that provide power to many businesses...
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Badal Shah

View Badal Shah's Profile
About: Badal Shah, managing director and CEO of Flareum Technologies, has more than a decade of experience in clean energy. His career in the clean tech sector began i... more »

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