Bioenergy, Geothermal, Solar, Wind Power

Producing Clean Power in the Absence of Water

It’s hard to go on a water-free diet when you’re a manufacturing facility, pushing out exhaust heat at more than 400 degrees Fahrenheit. Sure, a solar field or a wind turbine could generate water-free clean energy, but I’m not talking about them. I’m talking about the lumber mills, the cement plants, the utilities, the steelworks and all of the other facilities that already exist and serve as the backbone of American industry.

Every manufacturing process requires heat to produce materials and goods. And the cheapest and fastest way to cool that heat down is through water; more specifically, steam generation. The good news is that all of the fast moving water that’s heated to steam flows through a turbine generator and actually produces energy that is fed back into the process. This is known as a condensing turbine, which uses steam to recover energy. The bad news is that according to the U.S. Geological Survey, almost 2,300 gallons of water are wasted for every megawatt hour of energy generated.

Fresh water is one of our planet’s scarcest natural resources. According to the National Renewable Energy Lab, thermoelectric power alone accounts for 39 percent of all water consumption in the U.S., consuming over 200 million gallons per day. And the majority of that water is used to cool our heated power-production equipment.

But why are manufacturing facilities using water to cool their systems when there has been a water-free technology in existence for more than 50 years?

The water-free technology I’m referring to is the organic Rankine cycle (or “ORC”), which traces its roots to the geothermal power generation sector, where it was first popularized in the late 1960s. These systems operate on the same basic principle as the traditional steam cycle with two notable exceptions: ORCs use a contained organic working fluid (typically an environmental refrigerant) instead of water, and ORCs do not require water for cooling.

ORC that takes all of that exhaust heat and cools it using an environmentally benign refrigerant. The refrigerant moves through a closed loop system, turning from liquid to steam and back to liquid again. It produces continuous power, is completely self sustainable and has a lifespan of at least 20 years. And despite its long-standing popularity in Europe, with over 100 working installations, the technology has suddenly begun to rise in popularity in the U.S.

Historically, industrial operations haven’t had to worry much about the availability of water or the regulations pertaining to the precious natural resource. But things are taking a turn.

Public attention continues to grow around the issue of water scarcity. Its status as a precious resource is forcing power plant developers to absorb new and higher costs as they wrestle with water permitting authorities to bring projects to fruition.  This translates into higher power costs for all customers – both industrial and consumer alike.

The good news is that public awareness of ORC is rising quickly. In particular, industrial and power plant operators have accelerated efforts to work with project developers on ORC-based “waste heat recovery” systems. Across the nation, more than 25 projects have already been completed by a number of developers, with many more in the pipeline.

These waste heat recovery projects harvest the excess thermal energy that is typically vented into the atmosphere by cooling it and repurposing it for power generation. It is the use of organic working fluids with low vapor points and high molecular densities that makes this possible. 

Steel mills, power plants, oil fields, cement plants, paper mills, and refineries are just a few examples of large industrial facilities that have both usable waste heat and a large appetite for electricity. Through the use of ORC-based waste heat recovery, these operations are quickly and easily reducing their demand for the traditional water-cooled steam plants – putting water savings in the millions of gallons per year. And on top of that, the byproduct is clean energy that feeds directly back into the plant, pumping out power in the megawatts.