Tri-Generation Is Environmentally Friendly

“Great Northern Hydroponics signs a 20-year government contract for generation of the 11.5mW of electricity”

Producing more than 22 million pounds of tomatoes each year, in a 50-acre greenhouse is no small task, and being environmentally-friendly about it is even more impressive.

Traditionally, tri-generation refers to burning of a fuel, such as natural gas, to get electricity, heating and cooling. In the case of Great Northern Hydroponics (GNH), they are a natural gas-fired 12mW tri-generation facility burning natural gas and getting electricity, heat, and CO2 in return.

Ontario, Canada-based GNH, a division of Soave Enterprises, signed a 20-year government contract for generation of the 11.5mW of electricity. Under the contract, the Canadian government is purchasing the electricity generated by the plant – enough to power 5,000 residential homes in the local area. The GNH’s tomato crops, their energy costs, and the environment as a whole will benefit a ton – literally. The facility cost about Cdn$20 million to complete; however, the greenhouse will save a minimum of 50% of its energy costs over the next 20 years and will capture 15,000 tons of CO2 – which would normally go into the atmosphere – for the fertilization of their tomatoes.

“The objective of this entire project is to bring down our cost of heating the greenhouse, and it’s critical to the survival of the greenhouse industry in the next 20 years,” says Darrin Didychuk, president of GNH.

Greenhouses require a substantial amount of heat to grow plants, and the rising cost of natural gas has really been crippling the industry, which is why Didychuk, along with General Manager Guido van het Hof, spent two years researching and developing this project – and working to make it most beneficial to everyone involved.

It began when Ontario Power Authority (OPA) came out with a request for green energy projects. Didychuk and van het Hof lobbied them to allow commercial greenhouses to qualify under the district heating segment; utilization of CO2 emissions also enables them to be a carbon sink. When CO2 is reabsorbed back into the land, it is referred to as a carbon sink.

A natural direction was to look toward the greenhouse industry in Europe, which has been using co-generation and CO2 fertilization systems for more than a decade, and GE Energy has supplied well over 500 of these systems.

Breaking it Down

The technology is a natural-gas-fired heat and power project that provides electricity generation, hot water, and carbon dioxide to the greenhouse. Creation of electricity from natural gas produces substantial amounts of thermal energy, as well as carbon dioxide exhaust emissions. Being a tri-generation facility, GNH burns natural gas in four GE Jenbacher reciprocating gas engine generating units with selective catalytic reducer (SCR) emission controls. This thermal energy – in the form of hot water – is then supplied to GNH to heat the green house.

Next is employing the latest in environmental technology to clean the exhaust emissions and to extract carbon dioxide, where the carbon dioxide is the key component of photosynthesis – providing the greenhouse with the necessary fertilizer for the greenhouse’s tomato crop. Since the CO2 is not emitted into the air, GNH is also looked at as a net user of CO2.

The third component is the electricity that is generated by the engines and transferred to power local homes. “The project represents the only one of its kind and is currently the most technically-advanced and environmentally-sustainable project of its kind anywhere in North America,” Didychuk explains.

The entire system was co-designed between and GNH. “We sourced and imported all material with the generating equipment designed and imported by GE,” Didychuk says. “We acted as our own project manager and general contractor. However, having an industry leader as your technology partner, such as GE Jenbacher who dominates the European greenhouse industry with a market share of greater than 70% really helps the success of a project like this.”

Inner Workings

Jenbacher Type 6 engines are reliable, advanced products serving the 1.8mW to 3mW power range. The 1,500rpm engine speed results in high power density and low installation costs. The Type 6 pre-combustion chamber achieves maximum efficiency with low emissions, and the proven design and optimized components enable a service life of 60,000 operating hours before the first major overhaul. Pre-chamber combustion ensures maximum efficiency while the turbocharger bypass evens out extreme operating conditions. The external dry exhaust manifold ensures long cylinder head life, and the selective knocking control for each cylinder ensures optimal protection.

An un-cooled exhaust gas manifold enables maximum energy supply to the exhaust gas turbocharger. The cross-flow cylinder head utilizes the cross-flow principle of gases through individual cylinder heads. Integrated into the cylinder liner to prevent carbon deposit on the piston crown is the scraper ring. The Gas mixer works according to the equal-pressure principle and has been steadily optimized to meet the requirements of modern gas engines.

The Turbocharger bypass, an electronically-controlled valve installed behind the compressor, enables fast output control in the upper load range. DIA.NE XT, engine management system, comprises powerful central industrial controls that handle master control and feedback control for the engine-plant, as well as visualization. LEANOX is GE’s lean mixture combustion control which ensures the correct air/gas ratio under all operating conditions, minimizing exhaust gas emissions while maintaining stable engine operation. The electronic ignition system is a microprocessor-controlled ignition system which is connected to DIA.NE XT via CAN (controlled area network) bus.

Future Growth

Besides the energy savings and the environmental benefits, tri-generation is also improving tomato production. Didychuk tells that the lifespan of a greenhouse tomato is short – about eight weeks from flower to picking – so you really need to capitalize on your growing time. “Injecting the captured CO2 into the greenhouse, where it then flows out to feed the tomato plants, is an extra boost of fertilization that helps the plants grow larger and faster.

“Staying ahead of innovation with even more energy solutions isn’t easy, but we plan to add cooling to the process within the year, turning it into a quad-generation facility, which is a really unheard of and rare occurrence,” Didychuk states.


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