The US: Lagging in Renewable Energy, Leading in CO2 Reduction

Anytime the topic of green energy comes up, Republicans think Solyndra and Democrats think jobs. The Republicans think of a failed government intervention that cost the taxpayers money and the Democrats think of flourishing new industries making solar panels.

Solar farm on a wind farm: Philippines 

Both really should think about climate change and how to reduce carbon emissions. The urgency of that is driven home month after month of news that confirm the worst predictions of climate researchers regarding the negative effects of global warming, namely in terms of sea-level rising, storms, shifts in precipitation, polar ice melts and impacts on flora and fauna.

How can green energy reduce carbon emissions, or more specifically, how does a post carbon energy system look like? What works and what doesn't? The answers are far from obvious. Most assume that a large part of the reduction has to come from electrical energy production which according to EPA contributes with 30% the largest share of greenhouse gases in the US. The reduction would come from a switch from coal, oil and gas to the tested renewable sources of solar and wind.

Will a low emission electricity regime consist of millions of solar panels all across America supplemented by thousands of on-shore and offshore windmills linked in a giant network all across America?

EPA Emissions pie chart

Or will the energy future be one where more and more energy users will go off the grid and supply for their own demand or even deliver energy into micro-grids that are fed entirely by renewable energies such as solar wind and, maybe, hydrogen?

Neither future is easy to achieve not only because of the disruption it would bring to the energy sector and the oil, gas and coal industries but also because renewable energies have their own set of technical problems that have mostly to do with the grid and how to balance supply and demand. It is necessary to understand some of those issues.

The Grid

The US energy grid isn't nationwide (it consists of three networks) and it was installed to bring electricity from large energy producers and power plants to the urban centers where most energy is used. The grid is ill equipped for "back feeding", i.e. consumers supplying energy in a two-way system. The grid also

The three power grid zones (source)

isn't structured to bring energy from sea-shores or mountain tops (wind) or sunny deserts (solar) to urban centers. That;s just not where the lines are. Running large new transmission lines across the nation is so exceedingly difficult due to local opposition that various US project for new lines were abandoned. In Germany construction of new transmission lines lag so far behind new wind installations that the wind turbines have to be switched off because their power can't get to distant consumers. Unlike the American grid which doesn't cover the entire continent, though, the European countries are largely interconnected making a large scale black-out or failure less likely.

Sagging and overloaded: The future of the power
grid is murky (photo: ArchPlan Inc)

The alternative, of course, is a future without a large connected grid and distributed generation. I am not aware that anybody proposes this for a foreseeable future but the idea has been mentioned in the context of the frequently predicted hydrogen age in which hydrogen is a cheap and easy power source. Unfortunately, and in spite of a relatively widespread use of small fuel cells in buildings and some experimental automobiles and this year even in a train and an airplane, hydrogen is still energy consuming to produce, not easily stored and not widely available. As a result, "going off the grid" is more a concept for survivalists than a realistic energy plan.

Intermittancy

Unlike water that can just sit in pipes when the faucet is shut with a large reservoir somewhere on the other end providing capacity and pressure, electricity has to "flow", it can not be well stored with current technology and it has to maintain a  narrow range of  fluctuation in volume and pressure (Amps and Volts) so it won't fry the lines and the equipment along the way or at the consumer.

To avoid system failures, the amount of power flowing over each transmission line must remain below the line's capacity. Exceeding capacity generates too much heat in a line, which can cause the line to sag or break or can create power-supply instability such as phase and voltage fluctuations. Capacity limits vary, depending on the length of the line and the transmission voltage (Physics Today, 8/14)

In electric grids the energy supplied and the energy consumed (including line losses through resistance) need to be in balance. Anytime energy gets pushed into the grid from any power source it needs to be consumed somewhere. In a system with large centralized powerplants (there are about 3000 of those in the US) and a good record of typical consumption profiles this isn't as hard to achieve as it sounds. Utility company and energy providers distinguish between a base load and peak loads. Base loads are provided by large steady

transmission monitoring station

workehorses of power generation such as coal or oil fired turbines or nuclear power stations, both can't increase or decrease the amount of produced electricity quickly. For the instant response that is needed to pick up peaks or sudden lulls gas fired turbines are ideal or also hydro-electric plants where the water comes from artificial lakes high above the turbine that can release a torrent of water through large pipes at a moments notice. (In lulls, the extra energy can be used to pump water back up into the lake which essentially acts like a big battery). When it comes to renewable energy, the picture shifts drastically because wind and sun are intermittent, each supplier is comparably small and wind and sun can shift unpredictably within minutes. The increased variability and uncertainty of supply exacerbates a problem known as intermittency which fits ill with the desired steadiness of the grid.  The usual answer to the problem is to maintain conventional capacity as a back-up to renewables. In other words, renewable energy replaces conventional production not Megawatt by Megawatt. In fact, experience to date shows that renewables supply on average only about 30% of their installed power, in part because of the volatility of wind and sun and in part because even if they produce energy, there isn't always a matching demand and the supply has to be shut off. Many small solar suppliers learn this only after it happens to them and they read the fine-print in their contracts when they wonder why the solar cells don't earn as much as projected.

Increase and reduction of CO2 emissions. The US leads

Politics

The desire to increase the use of renewables has caused many governments around the US or the world to provide incentives for consumers to install their own solar cells or, in the case of farmers or foresters allow wind-farms on their fields and mountain-tops. Electric companies were mandated to buy energy at market or even higher rates. Sometimes these policies have created unintended consequences such as oversupply (frying the lines) and utility rates inflated by uneconomical subsidies. To date in the US these type aggressive push-for-renewables-policies were tepid compared to countries like Holland, Denmark, Norway or Germany, for example. Under Obama's "all of the above energy strategy a single focus has been avoided. Additional push for renewables is needed, though to reach promised emission targets. Initiatives for renewables have to be structured to solve the technical problems and  avoid the unintended consequences. For example, the ambitious Community Solar Program of the US Department of Energy.

With virtual Net metering, sometimes referred to as Solar Gardens or Community Energy Generating Facilities, an array of solar panels is placed in a field, or installed on the roof of an apartment building, a box store, or any place where there is good solar access.  A solar project developer obtains the land or building site, installs the panels, and then finds investors or subscribers to pay for the panels.  The subscribers likely live off site but get credit for the power generated by the panels they have purchased through a reduction in their home utility bill. (Community Solar, Maryland)

Projected solar energy production by country (source)

Will the US, with the help of this program run into the same situation as Germany, where rate payers for years have subsidized solar installation on the last roof to a point where the grid was almost fried by with wind and solar earlier this year ? Energy providers barely know what to do with all the energy without being able to shut off the cost effective baseline power generation that is needed to guarantee net capacity. As a result rate payers pay record rates and are in a near revolt.  Denmark and Germany are debating slowing their solar and wind subsidies.

World electric energy production by fuel: Renewables at the bottom

It is curious, that for all the heroic efforts many European countries have made in reducing fossil fuel in energy production, the US have actually achieved a higher carbon reduction than most of those countries.

Of course, the US did it through fracking which replaced a high emission fossil fuel (coal) with a lower emitting one (natural gas), a gain that was quick and effective but not only won't last, but also creates unwanted side effects such as high water consumption and contamination and even earthquakes. One of the side effects of fracking is also that energy prices took a nose dive, an event welcomed by consumers and economists but one that rewards all the wrong behaviors. Cheap energy discourages smart use. As a result, for the first time in years, driving (vehicle miles traveled or VMT) has gone up in the US and many other countries. So what is the right approach?

In light of so many questions and contradictions, it is obvious that people are confused and that the topic is almost never properly represented in the political debate, especially not during an election campaign.

Solar capacity: The US isn't even on the list

Conclusion

The reduction of carbon emissions is urgent and cannot rely on a continued benefit from the shift from coal to natural gas. The emission benefits from fracking are relatively short lived bonfires (most estimates put the energy bonanza coming from that technique in the currently known shale layers at around 20-30 years). For an energy regime that reaches Kyoto and Paris goals it is important to have measures in place that go beyond natural gas and are sustainable.

There is little evidence of  a sharp increase of renewable energy production in the US to date. A 2010 forecast provided by the engineering company Black &Veatch estimated that the US supply in 2034 will be about 50% natural gas, 23% coal and only 13% renewables with the balance as nuclear and hydro.

It is also important to avoid costly dead-ends such as installed windpower that cannot be used because there are no power lines (a current problem in Germany) or no techniques to balance loads.

US share of renewables and hydro in overall electric generation is small

Mitigation of the problems which are inherent in the use of renewable energy have to deal with the grid, the  penetration of renewables and the issue of environmentally friendly back-ups.

The installed renewable power and the grid have to be developed in lockstep. With increased penetration of renewable source in the power generation, the problem of variability and uncertainty increases, but not linearly. If a connected grid is large enough, the fluctuations coming from the day-night cycle and from weather variability begin to statistically cancel each other out except for rare times when it is night all across the country (no solar power), a huge weather system creates a nationwide wind lull (no wind power) but power demand is very high for some reason.  (usually not the case at night, for example).

Globally hydro leads all renewables: global overview

Back-up power from hydro plants can be environmentally friendly. Denmark (wind) and Norway (hydro) have a workable compact in which wind volatility can be effectively mitigated. Demand peaks and valleys can be flattened through smart meters and consumer attitudes in which high consumers of energy (air conditioners) are switched off for short periods in high demand peaks and flexible appliances like dishwashers and washing machines are turned on at night.
Large grid loops, for example around Lake Eerie, allow power overload absorption through running electricty in loops.

Technology may hold breakthroughs in electric energy storage, namely batteries and the eventually use of hydrogen fuel cells.

Most of all, though, energy demand in the highly developed countries has to be reduced through efficiency to make up for the growing demand in developing countries.

Klaus Philipsen, FAIA
updated 10/2/16

Guide to Community Solar
The US Power grid

Share: