Belgian Tomato Grower Slices Energy Costs
The Tomato Magazine
August 2006
SINT-GILLIS-WAAS, Belgium – The renovated
and expanded tomato-growing business
belonging to Geert De Breuck includes a
covered area of more than 27,000 square meters (six
acres), making it a large business for the region of
Sint-Gillis-Waas (Belgium). The facility produces
about 1,650 metric tons (3.64 million pounds) of
tomatoes annually with the help of an innovative
combined heat and power (CHP) system designed
and manufactured by Cummins Power Generation.
The system uses natural gas to generate electricity, heat and carbon
dioxide which are all used to accelerate the growth of the tomatoes.
The CHP system is the result of a direct partnership between the grower
and Cummins Power Generation. Cummins provided the equipment and technical
expertise for the CHP system as well as the bulk of the financial investment.
With a power system that operates above 90 percent overall energy efficiency,
as well as government regulations that grant CHP certificates and CO2
emission permits, the project is proving to be very economical.
Power system components
The centerpiece of the CHP system is a Cummins Power Generation model
GQMB 1.5 MWe lean-burn gas generator set. The generator is powered
by the Cummins QSV91G natural gas engine that has developed an enviable
reputation for high thermal efficiency, low exhaust emissions and high
reliability. The generator produces electricity that is mainly injected
into the grid; less than five percent is used on site.
Waste heat from the generator set’s water jacket and exhaust are
recovered via a heat exchanger and used to provide heat for the covered
plant-growing areas year round. A large buffer water tank was designed
to store heat produced during daylight hours. The heat can then be released
during the night to keep the plants warm. In addition to producing heat,
the generator’s exhaust gases are also a source of carbon dioxide
that the plants need for photosynthesis. A special exhaust gas washer
is employed to cleanse the exhaust before the carbon dioxide is used
to encourage plant growth. The system is housed in a prefabricated concrete
building measuring 11 x 12 meters (36 x 39 feet) which provides ample
room for maintenance.
Optimizing operation was a key to success
Optimizing the operation of the CHP system was a key to its economic
success, but this was often complicated by the needs of the growing
plants and the realities of operating a generator set. During daylight
hours in the summer, for example, the tomatoes need ample carbon dioxide
but require little additional heat. A CHP installation is better suited
for providing the carbon dioxide than a traditional gas-fired boiler,
however.
While a CHP installation supplies only half the amount of heat per
cubic meter of gas compared with a gas boiler, it produces an equivalent
amount
of carbon dioxide – plus electricity that can be used on site or
sold to the local utility. By only running the CHP system during daylight
hours, it produces carbon dioxide when the plants need it, and generates
electricity when its value is the highest. When heat is needed during
the night, hot water is circulated from the large buffer tank that was
warmed by the system during the day.
Other factors were also important to making the installation profitable
for the grower, namely system design, system efficiency and system availability.
In order to make the system economically feasible, the design team calculated
that the system had to operate between 4,000 and 5,000 hours annually – or
a little more than half of all the available hours. This required that
the generating system have an extremely high availability factor in addition
to having a sufficiently large heat-storing buffer tank to make efficient
use of the waste heat from the generator. Another key to the success
of the system was the exceptionally high overall efficiency of the Cummins
Power Generation generator and the heat exchangers. Compared with producing
heat and electricity separately, the CHP system realizes an energy savings
of about 25 percent.
Projected payback period of 3.5 years
While the financial performance of the CHP system depends on a number
of factors – the price of tomatoes, the price of natural gas, the
value of the electricity sold, the value of the government CHP certificates
and maintenance costs – the optimized system was designed to pay
for itself in about three and one half years. Gas prices tend to fluctuate,
but the selling price of electricity can be negotiated for up to three
years. At current gas prices, the sales of electricity alone pay back
a major part of the cost of the consumed natural gas.
For more than 80 years, Cummins Power Generation has been a major force
in increasing the availability and reliability of electric power around
the world. Its extensive global distributor network delivers innovative
power solutions for any on-site power need from remote prime power systems,
to clean, energy efficient cogeneration systems, to waste-to-energy power
systems that extend our natural resources. For more information on waste-to-energy
power systems, contact Guido Taymans, 1-877-769-7669 (US) or +44 1843
25500 (UK); by e-mail: energysolutions@cummins.com. Or visit www.cumminspower.com/energysolutions.
© 2006 Columbia Publishing
>> Return to top
Columbia Publishing & Design | 1-800-900-2452
www.tomatomagazine.com