Tdworld 2413 Windenergy

How Much Is Too Much in Renewable Energy?

Sept. 15, 2014
We have seen renewable technology growing faster than anyone had predicted, and that got me thinking about my introduction to wind.

Ain't technology fun? Thanks to tech toys like Skype and smart phones, it’s easy to stay in touch with friends, family and coworkers. Several times a month, my friend Rick Bush, T&D World’s editorial director, and I take a virtual coffee break together to discuss what’s going on. Recently, we got on the subject of renewable energy. We have seen this technology growing faster than anyone had predicted, and that got me thinking about my introduction to wind.

It was 2003 and, like most of my colleagues, I had heard about wind farms but had never seen one; they were not as plentiful as they are today. So I got really excited when my boss told me I was going to connect one to our utility’s transmission system. It seemed the utility, Public Service Company of New Mexico (PNM), had decided to go green.

Someone was going to build a 200-MW wind farm in eastern New Mexico. The developer had picked a spot where one of PNM’s bulk transmission lines was located. PNM was going to buy the output, and I was assigned to work with the developer. I would also build the interconnection substation for the wind farm. Building a substation was a piece of cake, but I was totally clueless when it came to the quirks of wind technology. I needed help.

As luck would have it, my friend Nick Miller works in GE’s wind energy division and is the guru for anything related to wind technology. I called Nick, explained my problem and asked him what he would recommend in the way of a crash course in wind generation.

The next thing I knew, we were meeting in a small West Texas town to tour a very large wind farm. The wind farm was a fascinating place with hundreds of GE 1.5-MW turbines scattered across the landscape. The tour was one of those proverbial “sipping-from-a-fire-hose” learning experiences, but Nick covered everything from the technology of the turbines to the idiosyncrasies of the ancillary systems.

Where Is the Wind?

A year or so later, the shiny new wind farm was in service, pumping electricity into the grid. Thanks to the wonders of technology, I could sit at my desk and pull up all kinds of information about the wind farm on my computer. I could track the output over any time frame that interested me.

What I saw was eye-opening. The electrical output from the wind farm varied a lot; consistency was not a strong point. When power was needed the most, the winds were calm, and when demand was at its lowest, there were gale-force winds.

A few years later, I left the utility and started my consulting company. In the time that followed, I worked on a couple more wind farms projects and picked up some solar experience, too. Interestingly, in the last few years, financial and regulatory incentives associated with clean energy have really encouraged the expansion of renewable energy. We now have gigawatts of wind on the global grid, but no one anticipated how photovoltaic (PV) technology would change the industry.

The price of PV has been dropping like a rock in the past few years while electricity rates have been soaring. In many parts of the world, renewables cost less than or equal to that of utility-generated electricity. As a result, our customers have installed rooftop PV in unprecedented numbers.

You might say people power has taken on a whole new meaning. Customers have transformed the tops of factories, warehouses and residential structures into urban power plants with their aggressive acceptance of rooftop PV.

It Is Manageable

Suddenly, some utilities have witnessed this rooftop technology morph from a curiosity to mainstream generation. PV has become a form of distributed generation, making feeders bidirectional and pushing net metering into the mainstream. It also has brought about some dicey operational problems linked to fluctuating voltages, volt/VAR issues and power-quality concerns.

Fortunately, several technologically sound remedies are available to the industry. Power electronics in the form of flexible ac transmission system (FACTS) controllers offer dynamic voltage support and the ability to continuously control the reactive power needs of wind and solar farms.

Another solution is the application of energy storage systems. Energy storage comes in mechanical, thermal, chemical, water or electrical schemes. These systems are available in capacities ranging from kilowatts to gigawatts. Their durations can be cycles or hours. In addition to addressing the aforementioned problems, energy storage makes wind and solar dispatchable by removing the intermittency from their output. That is really desirable in the quest to make renewables behave like traditional generation.

Some suppliers have gone so far as to combine FACTS devices with energy storage devices. This has given utilities powerful options in their goal to integrate large amounts of this variable resource into the grid, and make it reliable and dependable. With enabling technologies such as these, the question of how much is too much becomes moot. We can take all that is available.

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