Cogeneration systems can deliver the electricity, heat and supplemental carbon dioxide that controlled-environment growers can use to produce edible, ornamental and medical cannabis crops more efficiently and more profitably.

January 30, 2019

By David Kuack

The highest density of cogeneration systems in greenhouses is in the Netherlands. Cogeneration systems in Dutch greenhouses represent almost 25 percent of the electricity produced in the country.

“Cogeneration is a technology that converts natural gas into useful energy for greenhouses, which includes inside power generation to heat the greenhouses and the production of supplemental carbon dioxide that can be used to increase plant growth,” said Dick Kramp, founder and CEO of AB Greenhouse Power Netherlands. AB GPN is acting as a vertical cultivation center of excellence for the global AB organization. Over the last three decades AB GPN developed a standardized cogeneration solution for greenhouses which is fully integrated with the cultivation system.

“The cogeneration system purifies the exhaust gases to produce carbon dioxide. The carbon dioxide can be used to supplement atmospheric carbon dioxide for the production of vegetables, ornamentals and medical cannabis. For the production of cannabis, cogeneration is being used to generate electricity to operate the grow lights. Also, heat from the cogeneration system can be converted into chilled water to cool the greenhouses.”

The cogeneration system is based on the burning of natural gas.
“Fortunately natural gas is relatively cheap at this time,” Kramp said. “Right now cogeneration is the most economical way of producing energy. The founders of AB GPN started with this technology in Europe and have done over 1,000 unit installations in greenhouses.

“In greenhouses the two major costs are labor and energy. Cogeneration is an additional income stream by selling electricity to the grid and/or energy savings for growers to reduce their price of growing. To operate grow lights growers have to purchase electrical power from the grid. They have to have boilers to heat the greenhouses. They have to have chillers to cool down/dehumidify the greenhouses. With cogeneration on site growers can produce electricity so that they don’t have to buy it from the grid and they can produce the electricity themselves for a lower price. Growers save on their energy bill thereby lowering their cost of production. This enables growers to be more competitive.”

Greenhouse, indoor farm applications
Cogeneration systems can be used in greenhouses and in indoor farms.
“A cogeneration system is not just an engine and a generator,” Kramp said “It’s a total system that is integrated into a greenhouse or building. Ninety percent or higher of every Btu of natural gas is converted into useful energy. Cogeneration is the most economical way of converting natural gas into energy.

“With an indoor farm, it’s more energy intensive because it is not making use of sunlight. On the other hand, an indoor farm allows for the creation of its own climate because the building is more controlled. But it is more expensive to create that climate because it is not making use of the sunlight and grow lights have to be installed to light the crops.”
Kramp said the majority of greenhouse operations are using cogeneration to support the power that they cannot get from the grid.

“In Canada, we have sold more than 50 megawatts of cogeneration in Ontario,” he said. All of the cogeneration systems there are supplying power back to the grid as intermittent power.

“Cogeneration was driven by the need for flexible power supplied to the grid. There is a lot of wind-generated electricity in Ontario and there was a need for integrated flexible power. Cogeneration systems were installed in greenhouses to supply electricity back to the grid when it was needed when there was no wind.”

A vegetable greenhouse in California has a contract with its utility company to supply electricity back into the grid. The electricity generated by the company’s cogeneration system produces heat, carbon dioxide and enough electricity to power its 64-acre operation plus an additional 2,300 homes.

“This greenhouse is creating an income stream out of selling power to the grid,” Kramp said. “The cogeneration engines run during the day to produce electricity. The heat that is generated is captured and stored in a heat storage tank. This heat can be extracted from the tank at night when the engines are not operating. The engines also produce carbon dioxide that can be used during the day to increase crop productivity.”

Need for more electricity
Kramp said many medical cannabis growers in the U.S. and Canada are installing cogeneration systems.
“The biggest driver of cogeneration in this industry is the shortage of power,” he said. “Right now in the U.S. and Canada they are installing cogeneration systems because they cannot get the electricity from the grid that they need to light their crops. Many growers are installing cogeneration systems in order to guarantee that they have enough power.”
Kramp said growers who have installed cogeneration systems will see the value of the systems as the price of produce begins to drop.
“Currently growers are not really interested in reducing their energy bills by generating electricity at a cheaper price,” he said. “The value of medical cannabis will eventually decrease and will become a commodity like other crops. When it becomes a commodity, then the growers will have to lower their energy bills by installing cogeneration to stay competitive.”

Financial incentives
Kramp said the amount of money growers can save using cogeneration depends on the price of natural gas and electricity.
“Substantial savings can be achieved by installing cogeneration,” he said. “Depending on the price of gas, a kilowatt of electricity can usually be produced for a lower price than buying it from the grid. It really depends on the price of natural gas. The exact savings will be determined in a feasibility study that is done before a cogeneration system is advised.”
In addition to the savings that growers will realize from generating their own electricity, Kramp said many states offer financial incentives for installing cogeneration systems. Both the U.S. Department of Energy and EPA promote incentive programs related to cogeneration, which is referred to as combined heat and power.
“Each state has its own cogeneration program where there are different rebate programs available,” Kramp said. “The incentive program in Massachusetts is called Mass Save. The Department of Energy is supporting cogeneration. The agency has a special group that is available to do feasibility studies for growers interested in installing cogeneration systems.
“Massachusetts is also offering rebates for the installation of LED lights. To apply for these rebates a feasibility study has to be submitted. This is usually done by an engineering company. The state is only awarding the rebates when it is supported by a feasibility study that shows the savings from installing LED lights. Growers can work with the lighting companies to determine what types of rebates are available with the state. Combining LED lights with cogeneration is a great way to maximize efficiency.”

For more: AB Greenhouse Power Netherlands, (31) 631635065; dick.kramp@gruppoab.com; https://www.gruppoab.com/en/greenhouse.

David Kuack is a freelance technical writer in Fort Worth, Texas; dkuack@gmail.com.