Solar Air Drying and Cooling
Solar-heated air can be used for drying most crops that require
warm air. Solar heated air is ideal for drying delicate foods
since it will not burn or risk potential damage from high
temperature steam heat. Solar heat is non-polluting and best
of all, it incurs no fuel costs.
Existing commercial drying operations can be converted to
utilize solar heat by installing our system to pull heat from the building’s
metal roof or wall. We pull heat from under the metal panels,
add ducting and connect the ducts to the intake of the
drier fans. The system then pulls heated air from the underside
of the panels and passes the air to the drying chamber.
We install simple sensors in the air flow and use thermostatic
controls to turn off the incoming air flow when the temperature
is not high enough for solar heating. The existing system
then operates, as it always has, burning high-cost fuel but
serving the drying process.
For some in-field applications, we can use a ground-mounted
polymer system that is low-cost and very transportable.
In new buildings, our metal roofs and walls are integrated
with the building’s structure. We can retrofit a system
over almost any existing exterior wall or roof.
Solar-heated air can be used to dry:
- Crops, timber, distillers grains, and textiles
- Tea, coffee, beans, tobacco,
- Food for dehydration or processing
- Sludge, manure, and compost
Solar-drying systems can realize Internal Rates of Return
of 10-30% with a simple payback of as little as 5 years. Pay back will depend on the cost of the fuel being offset,
application, climate, design and scale. Tax credits can lower
payback periods for most commercial solar drying systems
Solar-Cooling. it's not the Heat it's the Humidity
The most energy-efficient cooling system uses the evaporation
of water to lower temperatures for building cooling and industrial
processes. However, thermal comfort in summer means more than
keeping the air temperature below 75° degrees F. High temperatures,
high humidity, or both can lead to excessive discomfort.
Water can be used to cool air to comfortable levels, until
the humidity levels get too high. When water evaporates it
absorbs a large amount of heat from its surroundings (about
1000 Btu per pound of water evaporated). The most familiar
example is the cooling effect of evaporating perspiration
on the human skin.
In hot, dry climates, body temperature is partially controlled
by the rapid evaporation of perspiration from the surface
of the skin. In hot climates with high humidity, the cooling
effect is minimal because the high moisture content of the
air prevents further evaporation. In those humid climates,
the most energy efficient way to achieve a cool environment
is often to lower humidity.
Traditional air conditioning systems must cool incoming air
to a very low temperature to remove humidity. The air then
is so cold the system must “re-heat” the air to
send 60F air into the space. The deep cooling and re-heating
uses more energy than simply drying, then cooling the air.
But most drying processes rely on expensive energy sources
such as natural gas, and electricity.
Our solar cooling systems dry air using low cost solar heat.
We pass air through desiccants to create dry air that supports
the evaporative cooling process. After leaving the desiccant,
the hot dry air is cooled in one side of a heat exchanger.
The warm, dry air is split into two air streams. The first
stream supports an indirect evaporative cooling of the second
stream. This cools the second stream without adding any humidity.
We regenerate the desiccants with low cost solar heat or a
combination of solar and other waste heat source so they can
be re-used continuously.
This system uses less electricity to produce cool, dry air
than a conventional air conditioning system. It is typically
used in conjunction with a conventional air conditioning system.
When solar or waste heat is applied, the conventional system
can operate at lower capacity, saving electricity. During
summer months, when excess solar heat is available, the systems
provide maximum savings during the hottest part of the day.
This is when the conventional system would be drawing the
most power and the electric rates are highest.
Solar heat can dry and cool
Solar heating is ideal for a variety of drying applications in agriculture and
Facilities can also use solar heat to dehumidify air in a solar-cooling system. Best of all, solar
heating costs less than other energy sources.