Renewables to spark U.S. grid revolution

April 17, 2009

John Kemp Great DebateGrowing power consumption and the U.S. administration’s plan to rely more heavily on renewable generation sources will increase the demand on America’s already overloaded electricity grid and require major investment in transmission and distribution networks.

Upgrading power transmission and distribution systems is likely to cost as much as installing new generating capacity over the next 20 years.

While Congress provided an extra $4.5 billion of funding for grid improvements in the recent fiscal stimulus, federal loan guarantees and other support, far more investment will be needed if the administration’s targets for renewable generation are to be realized.

In its “Annual Energy Outlook 2009″ (AEO2009), the Energy Information Administration projects consumption will increase by 1,000 billion kilowatt hours (26 percent) between 2007 and 2030. The United States will need to install 259 gigawatts (GW) of new generating capacity to replace aging generators taken out of service (30 GW) and meet increased demand on the system (229 GW).

A report prepared for the Edison Foundation by consultants Brattle Group last year put the capital cost of capacity installation at between $500 billion and $1 trillion (depending on how much of the total is met by cheap sources such as coal and gas and how much by expensive sources such as nuclear, wind and solar). Click here for PDF.

AEO2009 projects that most of the added generating capacity will be from conventional sources such as natural gas (53 percent), coal (18 percent) and nuclear (5 percent). But a substantial proportion will come from renewables (22 percent), raising the share of renewable power in total generation from 8 percent in 2007 (much of it from hydro dams) to as much as 13 percent in 2030.

The biggest additional contribution will come from the combustion of biomass waste products left over from increased production of ethanol to meet the federal government’s ambitious targets. The other major contribution will come from wind. Solar is likely to make a marginal contribution in the timeframe owing to high cost.

Biomass generators can be used in the same way as conventional power sources like gas and oil since the technology is identical (combustion to raise steam). The amount of power can be scheduled (“despatched”) to meet demand in exactly the same way as a conventional power plant.

Wind and solar present greater challenges because they cannot be scheduled with precision. As the percentage of power drawn from these non-despatchable sources increases, it will pose unique challenges for grid managers and require a substantial reconfiguration of the system.

Reconfiguring the grid to handle increased demand and a greater share of renewables will impose substantial costs. The Brattle Group report estimated the industry would need to spend as much upgrading the high-voltage long-distance transmission system ($300 billion) and lower-voltage local distribution networks ($600 billion) as it will on increased generating capacity.

GRID MANAGEMENT

Electricity supply is a relatively simple system in which power is supplied from generators to household and industrial appliances (“loads”) via the transmission and distribution network. But unlike other commodities, storing electricity is impractical, and supply and demand must balance continuously.

In response to short-term supply and demand fluctuations, system controllers employ a variety of techniques to ensure continuous balance between generation and load. In response to an unexpected increase in demand or loss of supply (caused by a generator tripping) the grid is rebalanced by a multi-tiered process:

– In the first instance, shortfalls are met by drawing a small quantity of additional energy from each of the remaining generating units on the grid. But while this automatic response provides compensating power for several seconds, it causes generating units to lose momentum and electrical frequency to decline across the grid.

– In the second stage, loss of frequency is sensed by governors attached to each generating unit on the grid causing them to deliver more fuel to the turbines, re-accelerating the generators. Producers are paid a fee to operate at slightly below full capacity to provide these frequency reserves, which are available within as little as 10 seconds and last up to 30 minutes.

– Beyond frequency reserves, the grid can call on “standing reserves”, typically gas-fired peaking plants held on stand-by that can be started rapidly and begin delivering extra power within 20 minutes.

All these responses focus on generation. But in the last resort the grid can begin “load shedding” (cutting off the power to some users to limit the demand on the system). Traditionally, certain industrial users receive power on “interruptable” contracts that allow the grid operators to instruct them to reduce their usage by a specified amount during an emergency.

In future, the industry hopes to develop dynamic demand control (DDC) systems allowing the grid to “defer” less sensitive loads (particularly refrigeration, air-conditioning and heating) by switching them off for a few seconds or even minutes at a time until more standing reserves can be brought online.

DDC would be triggered either by fitting appliances with their own frequency-sensitive governors or installing some two-way communications system.

INCORPORATING RENEWABLES

While loads from individual appliances are very variable and impossible to forecast, aggregate load from millions of appliances linked to the grid is much more predictable over a 24 hour cycle. In effect, the law of large numbers and grid interconnectedness help smooth the demand profile and make supply management possible.

In the same way, generation from individual wind turbines and solar units fluctuates significantly, but power availability becomes more stable if many different types of renewable energy (wind, solar, biomass) are connected to the grid at many different locations: strong sunlight and solar generation in the Mojave desert can make up for power lost when the wind stops blowing in Kansas.

Problems posed by variable power output from renewables can be managed in exactly the same way as variations in load or accidental loss of generating supply.

But as the percentage of renewable generation increases, so do potential imbalances. More renewables such as wind and solar will require more conventional (gas, coal and biomass) generating capacity to be held in frequency and standing reserve (potentially reducing efficiency and increasing cost).

Renewables proponents want to move away from the traditional power-on-demand model to one in which demand as well as supply is managed dynamically. If load as well as generation can be scheduled, via “smart grids” and other control techniques, the amount of generating capacity held in costly reserve could be reduced.

Increasing renewables will also put a premium on long-distance transmission capacity so shortfalls in generation in one region can be made up from increased output in other areas. But the U.S. power grid grew up piecemeal and is plagued by bottlenecks. In particular, there are limited interconnections between the eastern and western United States across the Rocky Mountains, and between Texas and the rest of the country.

Bottlenecks are already causing reliability problems, which will worsen as the percentage of renewables increases unless grid capacity is upgraded.

The fiscal stimulus approved earlier this year directed the Department of Energy to provide technical assistance to help increase transmission capacity across the Rockies and with Texas. But grid management will have to undergo a revolution if the share of renewables is to be raised significantly without an adverse impact on reliability.

Much more investment, and more federal government support through direct funding, loan guarantees or favorable charging regimes will be needed if the renewables aspiration is to be made a reality.

27 comments

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would someone who understands the issue comment on the vulnerability of the grid to a solar plasma event and its relationship to diversification. thanks

Posted by walt hauschildt | Report as abusive

I’m not an electrician or electrical engineer. Just as a wild guess off the top of my head, I suppose if we ground different degrees of rotation and create ionic bridges in the soil, there might be offsetting differentials that can contribute to brownouts. The same is true with the atmosphere if it becomes more conductive since transfer voltages are generally quite high – such as 10,000 volts – leading to a greater likelihood of jumping. It will be a good read when somebody corrects me as far as these plasma events. I’m not sure how many plasma people read these articles.

But diversification is positively critical to survive any kind of prolonged power outage. I remember when we lost power for a few days one summer and lost everything in the refrigerator. It is far worse though losing heat in the winter. Electrical infrastructure is getting old. We are placing heavy demands on what we have. We are using more power not less. Plus we have placed our faith in computer control systems with lots of complicated software coding. If we could canvas the cities of tomorrow to learn what triggers all the electrical loads and when, develop adaptive algorithms to automatically adjust, we might be okay. But just by accident we can get hit by the electrical version of a rogue wave. We could be under attack and not even know.

Posted by Don | Report as abusive

John,
Thanks for raising this topic. It seems to have triggered an active debate with a lot of factual information, which bears testimony to the fact that current worries are indeed extremely actual and deserve far more attention that they get. It is amazing to see how comments posted reflect that many people may be looking at the same issue at the same time with vary different angles. Sometimes, one would hope, and preferrably sooner rather than later, this could result in a democratic drive providing new directions to studies, solutions and budget spending of the world economies. One of the key issues is probably: how to convert millions of unformal individual debates such as this one into concrete influence on policies for realistic goals to be set,respected and translated into law? I particularly liked the comment of one of the readers on university / teaching. Such topics should become widely taught by praticians and theoricians of the field to educate more engineers and generate the brain resources that will have to carry on research on the topic in the next decades. If massive amounts have been spent on space exploration related projects in the 50s and 60s culminating with man being sent on the moon (was it really needed?), one could hope that at least a similar attention and money would be devoted to environment related energetic issues (for which solutions are badly needed to preserve human life). All the more so as money spent on research and its applications, new industrial sectors and education with identified objectives and adequate budget monitoring is seldom money badly spent.

Posted by Pierre Henri | Report as abusive

The privatized utilities want the government to pay billions to upgrade them into this super consolidated network, how about a simpler route, they make their connections easier and smart, and smart vehicles take energy when there is surplus and intelligence and information visibility substitutes near term for an expensive network (electricity itself has no intelligence).

Sometimes simpler and decentralized is easier, so smart meters might improve things quite a bit, and information on rates and capacity timing so the devices react to the network and not the other way around

Don’t mean to snub the people who are contributing to the debate, but unfortunately, it doesn’t seem many people who’ve posted actually is in the industry. And we talk facts.

If we continue our reckless fossil fuel burning rampage, eventually we’ll run out.

Till then, fossil fuel prices will be pushed up, and they will be passed onto the consumer.

It will be beneficial for the consumer to try him/herself to start making real changes, how soon, time will tell.

They’ll be pressure on the governments to start to act, and by then it’ll be likely too late. There WILL be an energy crisis in the next 30 years, or maybe a bit further down the line, but it’ll come.

Someone posted an article whom the writer is an expert on the matter, and it just can’t be done.

We can’t meet future energy expections without more salvaging of fossil fuels.

Scientific breakthroughs will come, and maybe if we’re lucky perhaps the golden egg to our woes.

So, till then, just keeping ringing your providers and asking them why your bill is extroadinarily high.

Posted by Alabarmy | Report as abusive

what is wrong with the idea of solar/wind/geothermal energy production distributed throught the housing industry. Let new homes be constructed with these built in and the government can give rebates on older homes to convert. In much of the south and west these homes produce more power per year than they use. The excess could be sold to business and provided to a developing electric transportations industry. I could be way off base since I am no expert but, it looks like this would eleviate a lot of the stress on the current grid system.

Posted by B.Free | Report as abusive

One thing that will help us meet the goals presented is to conserve where possible. If you’re not using as much electricity to begin with you won’t need as much infrastructure. In my own apartment I did knock down the electrical usage by one seventh, and we’re a family of five. If the government further encouraged conservation they could lower the cost to be invested by a similar amount.

In my case, why I started on the route to conservation to the extent I have is saving myself money. It pays off big time. Our budget isn’t as stretched as it would have been otherwise. More savings have also been realized by turning down the thermostat, installing LED nitelights and other technologies. Saving money on the utilities has allowed me to further invest in even more items that save money, like NiMH batteries.

Posted by Brian Bigelow | Report as abusive