Seeking green power solutions for hazy days

Portland General Electric got a lesson in one of the shortcomings of renewable energy last week.

With temperatures above 100 degrees in Portland, the company broke its all-time record for summer power consumption Monday, then again Tuesday, and also on Wednesday.

All the while, the companys Bigelow Canyon Wind Farm 140 miles east of Portland was producing next to no power. The winds that usually suck cool air up the Columbia River and keep summers mild had ceased, baking Portland and idling the turbines at Bigelow Canyon just when they were most needed.

If wind and solar are going to play a bigger part in meeting the countrys electrical demand, utilities will need to get faster at reacting every time the wind dies down or a cloud moves in front of the sun. Bends PV Powered is working on solving a part of the problem.

The federal government recently awarded the company $3 million to get to work building the machines needed to create a future network of thousands or even millions of small-scale solar generating systems.

The Solar Energy Grid Integration System is an initiative of the Department of Energy that seeks to make solar power cost-competitive with other forms of power generation by 2015. Right now, solar power makes up only a tiny fraction of the total energy consumed in the United States, but that could change quickly if current trends continue.

According to a 2007 Energy Department report, 5 to 10 percent of electricity customers could be using some form of solar power within 10 years if homeowners continue adding solar panels to their homes at the current rate.

In 2007, the Oregon Legislature passed a law requiring the states largest utilities to generate 25 percent of their power from renewable sources by 2025. Several other states have adopted similar goals.

Steve Hummel, vice president of engineering for PV Powered, said the goals are attainable, but only with a coordinated effort involving the government, the American people, the utility industry and companies like his.

Obama has said we need a man-on-the-moon type of effort to do it, and I believe hes right, Hummel said.

Moving from large hydroelectric dams and coal- or gas-fired power plants toward rooftop arrays of solar panels or small stands of wind turbines has potential advantages for the individual consumer, but for the utility industry, its a potential headache.

Distributed generation, as its known, would allow a homeowner with a home solar system to use the power from a utility at night, and sell excess solar power back to the utility during the day, effectively running the electric meter in reverse.

For the utilities, renewable energy means uncertainty a sluggish wind turbine cant be turned up, and a solar panel cant be quickly moved out of the shade. Its estimated that if such sources are used for as little as 5 to 10 percent of the total power supply, brownouts and blackouts could occur when they inevitably stop producing electricity from time to time. When the generation is distributed across a large area and is subject to different weather patterns rather than concentrated at a single plant predicting the spikes and drops in the current and reacting accordingly becomes even more difficult for utilities.

The problem, Hummel said, will likely be solved by building a better inverter, the device produced by PV Powered. If the company succeeds in building that better inverter over the next year, its likely to receive another $3 million from the Department of Energy in 2010 to help bring it to market.

Improving todays technology

An inverters primary purpose in a home solar generating system is to convert direct current electricity into alternating current, the type that runs lights and washing machines and consumer electronics. The inverter also manages the two-way flow of power, sending electricity into the grid when the home system produces a surplus, and drawing electricity from the grid when the home system is generating too little.

Current inverter technology is adequate for providing supplemental solar power to a home, Hummel said, but is ill-suited for coordinating hundreds or thousands of home solar generating systems to help power the grid as a whole. When an inverter detects fluctuations outside a narrow range in the current flowing in from the grid, it shuts off automatically to protect the system, much like a circuit breaker or a power strip. If, for instance, a high level of power usage creates a voltage drop within the grid, all of the solar generating systems connected to that grid could be shut down, further reducing the available power and increasing the risk of brownouts or blackouts.

Its very crude. If (the current) is outside of the acceptable voltage and frequency range, it goes down, Hummel said.

Erick Petersen, the vice president of sales and marketing for PV Powered, said the governments willingness to fund exploration of how to solve this problem is encouraging for people in his industry.

Its one thing to say we want to put renewable energy out there its another to sit down and go, If we do it, what happens? Petersen said. So all of this money is going to address some of the fundamental challenges, and create new technology that doesnt exist today to go with this mass deployment.

The goal for PV Powered, Hummel said, is to create an inverter that can talk to the grid more effectively, and better react to the needs of both the generator or the building it serves, and the grid as a whole.

With a smarter inverter, a home with a solar generating system could maintain constant communication with the utility company, monitoring the price of electricity for sale or purchase in communities where prices fluctuate to reflect demand, as well as weather forecasts, and past patterns of power usage in the building it serves. This information could allow the inverter to independently decide when to sell, buy or store power, while the utility company would be able to better predict how much power it can draw from the distributed solar generation system.

Making the transition

Hummel said its likely improved inverters will first be used by utility companies, improving the efficiency of converting solar energy into usable electricity at solar farms, and helping to better manage power generated at wind or solar farms. When a cloud moves over a solar farm, a more sophisticated inverter could detect the drop in power generation immediately, cueing a coal, gas or hydropower generator elsewhere to step up production.

PGE spokesman Steve Corson said that while the Portland utility is pursuing renewable energy sources, even though technical limitations and their unpredictably prevent them from providing a significantly larger share of power production today. The utility is a partner with PV Powered in its grant-funded research and will be helping test whatever products the company develops in a yet-to-be-determined Oregon community next year.

I think theres a little bit of a misperception out there among many in the public that this is a simple trade-off you can get rid of some of these older fossil fuel resources and simply bring on new renewables and energy efficiency, and youre good to go, he said. And the reality is, while there are certainly advantages to these resources, there are also significant challenges in how we manage those resources, and sometimes they simply are not going to produce.