Solar Air Cooling
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Solar Air Cooling
Date Introduced in the market:
Maturity of the technology:
Some projects implemented, Research and development continue
Status of development:
Commercially available for industrial and commercial applications, testing and demonstration projects underway for smaller systems. Research and development is ongoing.
Solar assisted thermal cooling is currently primarily a demonstration technology with a few commercial/profitable applications to date. Research is ongoing to improve efficiencies and reduce costs.
Type of energy that can be produced (i.e. thermal, electrical):
To provide thermal energy to assist thermal process space cooling systems.
To reduce the use of gas, electricity or other fuels in conventional thermal cooling systems.
Thermal cooling systems used with solar thermal energy include absorption cooling, desiccant cooling and heat engine/vapour compression cooling.
Thermal cooling systems are typically found in large industrial, commercial facilities such as hotels, office buildings, factories and warehouses.
Current solar assisted thermal cooling systems are significantly more expensive than electrical cooling systems. Research is ongoing to improve efficiencies and reduce costs.
Range of possible dimensions and sizing considerations for the system:
Solar cooling systems are typically used in industrial or large commercial applications with a significant cooling load. Combining solar cooling systems with a year-round solar hot water system increases efficiency. The main components of a Solar cooling system are the collectors, storage tanks and the thermal cooling system. Typically, glazed flat plate or vacuum tube collectors are used depending on the temperature required for the thermal cooling system. Where higher temperatures are required (above 80degrees Celsius), vacuum tube collectors are usually used.
Where thermal cooling systems use water to provide cooling, about 3m2/kW of collector area is needed. Where air is used, as in desiccant coolers that provide cooling through dehumidification, a collector area of about 10m2/1000m3/h of air volume flow is needed.
Factors taken into account when sizing a solar thermal cooling system include; cooling load, design of the thermal cooling system, combinations with other systems (e.g. solar water heating), climate and solar exposure.
Range of performance of the technology per unit installed:
In Canada, solar hot water systems produce approx 500-1000 Kwh/m²/year Kwh or approx 1.8 - 3.6 GJ/m2/year
The performance of thermal cooling systems is measured by the relationship between the heat driving the processes and the realized 'cold' energy, called the coefficient of performance, or COP. A higher COP means a more efficient process. Typically, the COP of solar assisted thermal cooling processes range from 0.6-1.2.
Range of costs per unit of energy and per system (installed, and maintenance costs):
Current solar assisted thermal cooling systems are significantly more expensive than electrical cooling systems.
Design, Installation, Maintenance & Operation of solar cooling system:
Design of a solar cooling system:
Expertise/knowledge required can include: HVACR (heating, ventilation, air conditioning and refrigeration) design, solar design, plumbing, electrical, mechanical, general construction.
Installation of a solar cooling system:
Expertise/knowledge required can include: HVACR, plumbing, electrical, mechanical, general construction skills, roofing.
Maintenance of a solar cooling system:
Maintenance depends on type of system.
Expertise/knowledge required can include: HVACR, plumbing, electrical, mechanical, HVAC system maintenance.
Operation of a solar cooling system:
Can be monitored and operated by building maintenance staff with instruction from contractor/installer. May require a certified HVACR practitioner.
Training for designers and installers:
For HVACR training, visit the Heating, Refrigeration and Air Conditioning Institute of Canada (HRAI), the national HVACR industry association (http://www.hrai.ca/). CanSIA is working with colleges to implement training programs for designers and installers of solar heating systems, based on the North American Board of Certified Energy Professionals SDHW certification. Training for solar cooling systems is not yet widely available. See www.cansia.ca for more information.
Range of Operational & Maintenance requirements (ex: how much labour time per week for how many people):
Operation and maintenance will depend on the type of cooling system the solar is assisting. The solar system requires only periodic monitoring and maintenance to ensure proper functioning. The thermal cooling system may require significant operating and maintenance time and skills.
Potential problems or challenges:
Solar assisted thermal cooling is currently primarily a demonstration technology with a few commercial/profitable applications to date. Research is ongoing to improve efficiencies and reduce costs. Because of the correlation between solar resource and cooling loads and the increasing demand for cooling systems, there is significant potential for solar thermal cooling systems. Efficiencies have been achieved but further research and development is required.
Investigate Maintenance contracts or warrantees.
Ensure system is designed for climate and cooling load.
Ensure southern exposure clear of obstructions between the hours of 10 AM and 3 PM or longer.
Most permitting offices will not be familiar with Solar Assisted Thermal cooling systems. Solar thermal permitting requirements are inconsistent across Canada. Be sure to enquire with your local permitting and planning office before beginning any project.
Range of warranties and life expectancy of the systems:
For the solar thermal system:
Warranties: 10 years
Life Expectancy: 20 - 30 years
Warranties and life expectancy of thermal cooling systems vary depending on the system. Contact a HVACR contractor for more information.
Solar Resources Assessment:
Site specific solar resources can be measured by visual techniques and inspection or through commercially available solar site analysis tools. The U.S. National Renewable Energy Laboratory has extensive solar radiation resource information at http://rredc.nrel.gov/solar/. Links to Canadian solar radiation data can be found at http://www.canren.gc.ca/resou_asse/index.asp?CaId=55&PgId=452
Inputs and outputs for the technology:
Solar Thermal collectors directly convert energy from the sun to useable heat energy. Heat produced by the collectors is transferred via a heat exchange fluid to a thermal cooling system.
A southern exposure unobstructed from the hours of 10 AM to 3 PM is preferred.
Anti-freeze solution and heat exchanger:
Many systems use an Anti-Freeze liquid (usually propylene glycol) and a heat exchanger to convert energy from the sun to useable heat energy. The anti-freeze solution usually lasts many years before having to be replaced.
Refrigerant or Desiccant:
Depending on the design of the thermal cooling system, a refrigerant or desiccant is used. Typically, the refrigerants used are CFC free and environmentally friendly, for example, LiBr (Lithium Bromide). Desiccants can be liquid or solid. Examples are calcium chloride, lithium chloride, silica gel.
Thermal cooling processes use about 0.25 - 0.5 the electricity of electric cooling systems. Solar thermal systems add some electricity use for the circulation pumps. Most systems have electric pumps that circulate propylene glycol through a pressurized closed loop. The amount of electricity required is minimal. It could be provided by the grid or by other sources such as a PV panel (see under "Potential combination …" for more detail).
Potential combination with other energy systems (hybrids and combination systems):
Water Heating and Space Heating:
The economics and efficiency of solar cooling systems are improved when combined with solar hot water and or solar air heating systems.
Photovoltaic (solar electric):
Solar cooling systems require electricity to run fans and pumps. While significantly less electricity is required than with a conventional electric air conditioner, it is not insignificant. Since the solar cooling system functions when there is a solar load, PV can be used to meet the electricity demands and allow the system to operate when the grid is not available.
Links to other sources of information:
- Canadian Solar Industries Association (CanSIA) - www.cansia.ca
- Natural Resources Canada (NRCan) - www.nrcan.gc.ca/redi
- Natural Resources Canada (CANMET) - www.nrcan.gc.ca/es/etb
- Canadian Renewable Energy Network (CanREN) - www.canren.gc.ca
- Renewable Energy Deployment Initiative (REDI) - www.nrcan.gc.ca/redi
- Solar Energy Society of Canada Inc. (SESCI) - www.sesci.ca
- Énergie Solaire Québec (ESQ) - www.esq.qc.ca
- Photovoltaic Energy Applied Research Lab (PEARL) - www.bcit.ca
- European Solar Thermal Industry Federation (ESTIF) - www.estif.org
- Solar Rating and Certification Committee (SRCC) - www.solar-rating.org
- Florida Solar Energy Center (FSEC) - www.fsec.ucf.edu/en/industry/testing/STsystems/ratings
- North American Board of Certified Energy Professionals (NABCEP) - www.nabcep.org
- BC Sustainable Energy Association (BCSEA) - www.bcsea.org/sustainableenergy/solarhotwater
- Natural Resources Canada PV and solar insolation maps - https://glfc.cfsnet.nfis.org
- Solar Energy International (SEI) - www.solarenergy.org
- International Energy Association Solar Heating and Cooling Program - http://www.iea-shc.org/
- The Solar Server forum for solar energy (Germany) - http://www.solarserver.de/lexikon/solare_kuehlung-e.html
Sources of supply (in Canada):
Check CanSIA's website for contact information for suppliers and installers in your area. www.cansia.ca
Énergie Solaire Québec sells for a small fee (free with membership) a list of renewable energy suppliers and businesses in Quebec. http://www.esq.qc.ca/
For information regarding Thermal cooling contractors and suppliers in Canada contact the Heating, Refrigeration and Air Conditioning Institute of Canada, www.hrai.ca
Recommendations on how to proceed with a project development:
Contact CanSIA: check their database for a local installer.
Finding a contractor: As when hiring any contractor, ask for references from other clients or examples of their work and past experience.
Contact your local building inspector and municipal permitting office.
Ensure you have the necessary permits and the inspector is familiar with your plans before construction.
Investigate potential government grants, incentives, tax rebates and financing programs at the federal, provincial and municipal level.
Check the links above for more information.