September 07, 2010
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Solar Drying

Technology Name:

Solar Drying

Date Introduced in the market:

1970s-2000

Maturity of the technology:

Mature

Status of development:

Research and Development ongoing with some commercial applications

Type of energy that can be produced (i.e. thermal, electrical):

Thermal

Typical applications:

To provide heated air for a wide variety of drying purposes
Crop, timber, manure and textile drying
Crop drying applications include tea, coffee, beans, tobacco
To dehydrate food for processing or preserving
To reduce the use of fossil fuels or wood burning in agricultural drying processes.

Expected Pay-Back:

Analysis of solar drying systems has demonstrated IRRs of 10-30% is possible with a simple pay back of 0- 5 years. Pay back will depend on the cost of the fuel being offset, application, climate, design and scale.

Range of possible dimensions and sizing considerations for the system:

Solar drying systems range from small box style dehydrators with capacities of less than a m³ to timber kilns with capacities of over 100,000 board feet to commercial scale barns where the entire roof or solar exposed wall is installed with a collector system.
Considerations for choosing a solar drying technology and sizing a solar drying system include the application, the desired temperatures, the volume of air flow required, climate, humidity and solar resource.

Range of performance of the technology per unit installed:

Perforated-plate solar collectors collect the equivalent of 1 to 3 GJ in energy per year and per m2 of collector. Most solar drying systems are used where desired temperatures is 50 degrees Celsius or below although higher temperature can be achieved with some design.

Range of costs per unit of energy and per system (installed, and maintenance costs):

Costs of systems will depend on the technology used. Small scale food dehydrators can be built for less than $100 with readily available materials. Solar kilns with board foot capacities in the thousands can cost tens of thousands of dollars.

For perforated plate solar collectors used in drying applications:
Installation costs:

Collector $100 to $250/m2
Ventilation system $0 to $100/m2
Where solar air collectors are installed on new building or when wall cladding is in need of replacement, the cost of conventional cladding is offset.

Design, Installation, Maintenance & Operation of Solar Drying System:
Design of a Solar Drying System:

Expertise/knowledge required can include: metal siding contracting, solar air drying system design, HVACR contracting, electrical, mechanical and general construction.

Installation of a Solar Drying System:

Expertise/knowledge required can include: metal siding contracting, solar air drying system design, HVACR contracting, electrical, roofing, mechanical and general construction.

Maintenance of a Solar Drying System:

Solar drying systems require usually low to virtually no maintenance. Solar collectors have low to no maintenance.
Expertise/knowledge required can include: metal siding contracting, solar air drying system design, HVACR contracting, electrical, mechanical and general construction.

Operation of Solar Drying System:

Expertise/knowledge required can include: principles of solar drying, HVACR operation.

Training for designers and installers:

Greater education and training opportunities for solar drying applications are needed. Some universities and colleges offer research opportunities. To date, much of the education has been done during installation and many systems in use were built by the users or demonstration projects. Some designs and plans are available on the internet and some drying systems are sold as a turn key operation.

Range of Operational & Maintenance requirements (ex: how much labour time per week for how many people):

Most solar drying systems require virtually no maintenance. Solar collectors have low to no maintenance.
Maintenance requirements will depend on the design and materials used. Operation of ventilation systems can be automated or manually controlled.

Potential problems or challenges:

Most solar drying systems are in the phase of research and demonstration in cooler, humid climates. While some systems are commercially available in Canada, they are not often considered. The lumber industry has a good potential for use of solar drying technology. Incentives, education and more local practical experience are needed.

Other considerations:

If you are purchasing a commercial solar drying system, investigate maintenance contracts or warranties.
Ensure system is designed for climate and drying needs.
Ensure southern exposure clear of obstructions between the hours of 10 AM and 3 PM or longer.

Permitting:

Solar drying systems are not yet included in most permitting and planning departments. Consult with your local permitting office before construction to determine what permits will be required if any.

Range of warranties and life expectancy of the systems:

Warranties: 10- 20 years
Life Expectancy: 20 - 30 years

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
Canadian Solar Resource maps are available at: http://atlas.nrcan.gc.ca/ and https://glfc.cfsnet.nfis.org/

Inputs and outputs for the technology:
Outputs:

Solar drying systems directly heat ambient air to increase its ability to pull moisture out of the air. The heated air is moved by convection, directed to drying fans or a ventilation system.

Inputs:
Sun:

A solar exposed wall or roof relatively unobstructed from the hours of 10 AM to 3 PM is preferred.

Electricity:

Many solar drying systems include fans to assist with the air flow. For example, the ventilation system that perforated-plate solar air collectors feed into may use fans and thermostatically or electrically powered bypass baffles. The amount of electricity used is based on the type of ventilation system and the amount of air flow required.

Potential combination with other energy systems (hybrids and combination systems):

Some solar drying systems double as wall or roof cladding.
Ventilation systems are usually incorporated into a solar drying system.
Photovoltaics can be used to power any ventilation electrical loads.

Links to other sources of information:

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/

Recommendations on how to proceed with a project development:

Contact CanSIA: check their database for a local installer.
Investigate potential government incentives. Check with CanSIA, NRCan, provincial Ministries of Energy and local municipal offices.
Finding a contractor: As when hiring any contractor, ask for references from other clients or examples of their work and past experience.
Ensure system designers are familiar with the drying needs, season and usually operation.
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.
Check the links above for more information.


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Created: 02-14-2008
Modified: 03-31-2008