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Waste Not

A Local Brewery Ups The Ante On Going Green



It's a cool, rainy summer afternoon in Cleveland, but several patrons still choose to sit in Great Lakes Brewery's open-air beer garden in Ohio City. The recently installed retractable roof has been pulled over their heads. Tempered-glass sliding doors, specially designed to keep out cold air in winter, stay open to let the breeze in. If it turns sunny, the roof will pull back entirely.

When fall comes, the roof and sliding doors will enclose the space like a cocoon. A floor with hot-water pipes running underneath will warm only the people and objects it touches, rather than outdoor air that might quickly blow away.

"The beer garden is a great example of green building principles," says Patrick Conway, co-owner of the brewery with his brother Daniel. "We can use it not just three months of the summer … but year round."

It's just the latest in the Conways' quest for "zero-waste" practices.

They've already tried vermicomposting (feeding kitchen scraps to worms to make fertilizer), run beer delivery trucks on used vegetable oil and fanned cold winter air into beer chillers. But to Patrick it's all been low-hanging fruit. A few dollars saved here, a little less carbon emissions and trash there. The biggest challenge has been the manufacture of beer, an energy-intensive production process.

"It was time to delve into more sophisticated technologies," says Patrick of deciding to tackle the dilemma. He quickly learned of a simple but little-known mechanism: waste-heat recovery. All one had to do was attach a heat exchanger to the brewery's exhaust pipe, which emits 600-degree flue gases from two giant boilers. Then, through an internal thermodynamic chemical process, an on-site waste-heat recovery device would use the high temperatures to produce electricity and heating or cooling.

"When our engineer explained this technology to us," says Patrick, "it was like putting wheels on luggage."

In January, Great Lakes will be among the first of four companies in Ohio to install an innovative waste-heat-recovery pilot project being developed by a high-tech start-up in Akron. The local brewery could cut its overall energy consumption by 750,000 kilowatt hours - or 20 percent, if not more. Annual savings could run into the upper five figures. And those numbers would only climb, if Ohio's electric utility regulations were to change for the better.When combined, the nation's small businesses, like Great Lakes, and large industrial factories, like steel mills and power plants, throw away thousands of megawatts of waste heat. If all this were to be recaptured and recycled through on-site devices, the power created would be enough to replace almost 130 coal plants and provide the country with nearly 7 percent of its total power-generation needs, according to recent studies by the U.S. Environmental Protection Agency and Department of Energy. The potential efficiencies - and market opportunities - are countless.

Akron-based ReXorce Thermionics, Inc. just received a $4.3 million grant from Ohio's Third Frontier Project, which funds innovative high-tech research to advance its work on waste-heat recovery. ReXorce is among a handful of outfits nationwide doing such research and development. The company's core product is the patented Thermafficient engine, which captures heat and turns it into electricity and heating or cooling. Heat sources include flue gases and the sun.

ReXorce focuses on lower-grade temperatures, all the way down to 220 degrees Fahrenheit, versus the 2,000-plus temperatures inside a steel-mill furnace. That's why this engine is able to run the waste-heat recovery unit that will be installed next year at Great Lakes.

At first glance, the demo device at ReXorce's headquarters looks like it was based on an M.C. Escher painting, with spiral pipes seemingly falling into each other. But it's a straightforward system that uses no new fuel and creates zero emissions. ReXorce's unique accomplishment is a liquid CO2 cycle in combination with a second fluid. Liquid CO2 has special properties that allow it to produce both electricity and cooling, and require less energy than water does to run a power-generating cycle.

A pump first takes the liquid CO2 to high pressure. Then a pipe interfaces with the heat exchanger, bringing in the high waste-heat temperatures. The CO2, now at high pressure and high heat, turns into something between a liquid and gas, called "supercritical." In this form, CO2 can be pushed in different directions to get either electricity and heat, or electricity and cooling.

Supercritical CO2 is then pushed through an expansion device. If the supercritical CO2 is connected to a turbine, which in turn is attached to a generator, it can produce electricity.

Hot, low-pressure CO2 gas must be cooled in order to start another waste-heat recovery cycle. The process of bringing the gas down in temperature can be used to provide heat. If a customer needs hot water, the CO2 gas can be run through another heat exchanger. Cold water that also loops through this exchanger will pick up heat.

On the other hand, when this CO2 is pushed through another nozzle, it will dramatically expand and drop in pressure. In this state, the properties of the CO2 gas make it want to pull heat out of anything it comes into contact with. For example, if you placed your hand inside this low-pressure tube, it would freeze. Pressure can be fine-tuned to achieve the desired cooling effect. So at Great Lakes, pipes carrying this expanded low-pressure CO2 will weave around the brewery's beer-chillers to cool them. When those chillers rise in temperature, the CO2 vapor will extract the excess heat away. Great Lakes' demo device will only be set up to provide cooling. (The brewery already has a natural-gas system in place for heating needs.) Even so, savings will be huge, says Joe Pustai, an engineer and energy consultant working with Great Lakes.

"Since we're not using extra electricity to create this cooling, but rather waste heat to get the same cooling effect," says Pustai, "we offset the power needs of Great Lakes."

Great Lakes, as a result, will maximize the fuel being burned - for high-pressure steam in its boilers and electricity production in a distant coal plant somewhere. And the brewery will offset that coal plant's carbon emissions by having decreased its own need for electricity.

Pustai estimates that through cooling alone, 750,000 kilowatts less electricity will be used in one year, a 20 percent reduction in energy consumption. That will equal savings between $65,000 and $75,000. If Great Lakes and ReXorce could turn on the device's electricity production feature as well, those numbers could more than double. For the time being, however, Ohio's regulations and Cleveland Public Power's archaic rate structures (CPP is Great Lakes' electricity provider) prevent recycled energy advocates and entrepreneurs from reaping waste-heat recovery's total benefits. "At Great Lakes, our unit will be able to produce electricity, but won't," says Philip Brennan, the chief operating officer at ReXorce. That's because Ohio law allows only licensed utilities to produce and sell electricity. Anyone else faces regulatory oversight.

Great Lakes could produce just enough electricity to meet its needs, and Ohio does have "net metering" rules in place that let locally produced electricity be subtracted from the power being pulled off the grid.

Privately owned utilities, however, usually discourage companies, large and small, from installing on-site waste-heat-recovery-based power generation by charging prohibitively high rates for backup power should the local supply break down. Such stand-alone power supplies threaten utilities' bottom lines. After all, profits are derived from costs passed on to users.

And costs are based on capital investments in far-away power plants, maintenance of a vast network of power lines that transmit electricity to urban centers, and a system of interconnects and hubs that deliver power to consumers. Commonly referred to as "distributed energy," such local, decentralized units of power generation would lower costs by reducing the need for much of the above.

Cuyahoga County recently considered on-site waste-heat recovery plants to power and heat its Cleveland government offices. The county is not within Cleveland Public Power's grid and so contracts with First Energy Corp., a private utility, for electricity. The deal-breaker was high standby backup-power fees.

Cleveland Public Power is more amenable to a matrix of distributed-energy power generation but is still navigating the learning curve.

"CPP wants to embrace waste-heat recovery - a distributed-energy landscape in general," says CPP Commissioner Ivan Henderson. "Our big question is, How do we incorporate customers with on-site power generation?"

The going is slow. For starters, CPP has no net-metering rates in place. The combination of all these factors means that Great Lakes must wait before it can produce its own electricity - and all consumers must wait before their utility bills go down.Great Lakes is an example of smaller scale waste-heat recovery. But it's dwarfed by the potential of Ohio's large-scale factories and manufacturing plants to recycle waste heat into heat and electricity. So with the enormous efficiencies and savings to be gained, why isn't more being done? See the August 20 issue.cgupta{A-T}clevescene{D-O-T}com

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