January-February 2013

Less Energy, More Conservation

Realizing the many benefits of CHP for water and wastewater utilities

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Photo: HOUWELING'S TOMATOES

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By Dan Rafter

When officials with Houweling’s Tomatoes installed two 4.36-MW Jenbacher J624 natural-gas engines in their Camarillo, CA-based greenhouse, they made history.

By installing the engines, Houweling’s Tomatoes became the first greenhouse grower in the United States to unveil a combined heat and power (CHP) greenhouse that captures carbon dioxide (CO₂) and uses it to fertilize plants.

But the installation wasn’t just about making history. Officials with Houweling’s wanted to operate their greenhouse as efficiently as possible. The CHP engines allowed them to do this, cutting the amount of power they consume, while also generating heat for the greenhouses and a fertilizer for the greenhouse’s plants.

Richard Vanderburg, energy and water conservation manager with Houweling’s Tomatoes, says that the CHP project allows the grower to burn fuel in the most environmentally friendly and efficient way possible. And for this greenhouse grower, that’s an important mission.

“We try to use everything we can when we’re providing power to our greenhouses,” says Vanderburg. “We’re committed to wasting as little energy as possible. This helps us meet that goal.”

Houweling’s is using the heat generated by the GE-manufactured Jenbacher engines to heat its greenhouses once temperatures drop at night. And they are using the CO₂ that the engines generate to fertilize the company’s world-famous tomato plants.

“It’s a very environmentally sensitive solution,” says Vanderburg. “Our goal has always been to burn fuel in the most efficient way. This allows us to do that.”

The workers at Houweling’s aren’t the only ones, though, who have discovered the many benefits of CHP systems. The manufacturers of these systems say that owners across the globe are increasingly recognizing the benefits that come with CHP.

Companies and building owners that invest in CHP systems can save fuel costs, because these systems capture the heat that they generate, heat that companies can then use in their facilities. Because CHP systems capture heat that would otherwise be wasted during the production of energy, these systems need less fuel than do separate heat and power systems to produce the same amount of energy.

At the same time, CHP systems are friendlier to the environment. Because CHP systems consume less fuel, they also produce a lower amount of greenhouse gas emissions.

Manufacturers of CHP systems have preached these benefits for years. And, they say, this preaching has steadily paid off: A growing number of building owners and companies are today realize that CHP can save them money while providing reliable power.

“More and more customers are starting to see that there is an economic opportunity in CHP,” says Nick Kelsh, business development manager in the electric power division of Caterpillar. “It’s a bit like SUV sales, though. SUV sales go up when gas is cheaper. We see the parallel there. When electricity prices are higher, more companies are interested in cutting their use of it. They are more likely to explore alternatives such as CHP systems.”

The demand for CHP differs by region, of course. In some parts of the country where electricity prices are higher—such as the Northeast portion of the country—the demand for CHP systems is rising. In parts of the country were electricity prices are lower, company officials and facility managers aren’t focusing nearly as much on the savings that CHP systems could bring them.

But Kelsh says that the overall trend is definitely pointing up when it comes to CHP demand in the United States and North America.

“The future trend, what the smart guys in the room are forecasting, is that CHP will grow,” he says.

Vanderburg, with California’s Houweling’s Tomatoes, says that he’s more than happy with the way the CHP system at his greenhouse grower has operated.

“The engine is working just as well as we had hoped,” he states. “It does need maintenance, of course. It needs the proper amount of attention to keep running. But so far, we haven’t had any major hiccups. The engine we have is pretty sophisticated.”

The engines have served as a more efficient alternative to the traditional boilers that the greenhouse once used to produce heat.

Officials with the Encina Wastewater Authority in Carlsbad, CA, don’t need to be educated on the benefits of CHP. They are already sold on the technology.

The authority, which provides about 350,000 customers in north San Diego County with wastewater treatment services, has relied on four G3516 engine generator sets from Caterpillar to provide about 71% of the wastewater authority’s power needs. The generator sets went into service in 2008 and 2009.

The authority powers these engines through biogases generated from an anaerobic digester designed to reduce solids in wastewater. The digester converts these solids into carbon dioxide and methane—biogas—that is in turn converted into reusable energy.

The generator sets are also flexible, able to run on both the captured biogas and natural gas. According to Caterpillar, on most days, three of the wastewater authority’s generator sets run on biofuel while one set runs on natural gas alone for four to eight hours during peak rate times.

The generator sets produce about 12 million kWh of electricity a year.

Octavio Navarrete, resource recovery manager with the Encina Wastewater Authority, says that the move toward a CHP system has been a financially rewarding one for his employer.

“The economics just made sense with a CHP system,” says Navarrete. “By going to CHP, we increased our energy efficiency. By generating our own power onsite, we reduced our electrical costs because we don’t have to purchase as much power from the utility. It has been a great benefit to us to have that reliable onsite power.”

This last benefit is an important one. One of the goals of the wastewater authority is to reduce its reliance on purchased energy. Specifically, the authority wants to produce 96% of its own power needs onsite by the year 2020.

The CHP system helps the authority get closer to that goal, Navarrete says.

“You can reduce your operating costs by producing your own power,” he says. “That makes a difference. The CHP technology has proven to be optimal for the goals that we are trying to reach.”

As always with a CHP system, little goes to waste in Encina’s power system. Thermal energy created from the cogeneration process is used to heat the authority’s anaerobic digesters. Thanks in part to this, the Caterpillar generator sets saved the wastewater authority more than $2 million in energy costs in 2010.

Results like this are important ones to the manufacturers of CHP systems. These are the success stories that, if manufacturers promote them properly, can provide an even bigger boost to the industry.

“It’s not just in the United States, of course, where you are seeing interest in CHP,” says Kelsh with Caterpillar. “In the last couple of decades, Europe has primarily been where we’ve been playing. But we are seeing more of shift now. We are seeing more of the growth in CHP coming in North America, too. That’s a good sign for the industry and its future.”

A wide variety of uses
CHP units today are used at a wide variety of building types, everything from data centers that will bleed valuable clients if they should ever lose power to hospitals and nursing homes in which power outages can be life-or-death occurrences.

In Bitburg, Germany, for instance, a CHP plant at the Bitburger Brauerei brewery has surged past 50,000 hours of successful operation. A GE Jenbacher J312 gas engine powers the brewery’s CHP plant. The engine converts biogas into electricity, steam, and hot water. It’s an example of how efficient the CHP process can be; very little is wasted in this application.

Since this CHP plant began operating in 2005, it has reduced CO₂ emissions by an equivalent of 10,000 tons. At the same time, it has provided the brewery with significant cost savings when compared to the steam boilers that the brewery previously used for power.

CHP systems have made a significant impact in Australia, too. In March 2012, an urban school district in Melbourne, Australia, installed a 2-MW GE Jenbacher gas engine to supply power, heat, and cooling. The gas engine here is expected to save the equivalent of about 9,000 tons of carbon emissions every year. To put that into more easily imagined terms, it’s like removing more than 5,500 cars from the road.

The cogeneration plant being used by the Dandedong Commercial District is designed to not only reduce harmful emissions but also to reduce the amount of energy that the district consumes. The plant can also produce surplus hot water. Cogent Energy, which built and owns the plant, can then sell this hot water back to local commercial buildings to provide cooling though these buildings’ absorption chillers.

So, not only does the CHP plant provide reliable and more efficient power for the school district, it also gives it an opportunity to make some extra money. That’s always important when school districts across the globe are facing budget cuts and tightening.

Author’s Bio: Dan Rafter is a technical writer and frequent contributor.