(The author is a Reuters columnist. The opinions expressed are his own.)
By Gerard Wynn
LONDON, Aug 22 (Reuters) - Natural gas could be the dominant power source for the next two decades in the western United States, even under the most aggressive climate scenarios, before making way for solar, findings from the University of California Berkeley suggest.
The Berkeley study examined the impact of cheap solar power, as envisaged by the so-called “sunshot” initiative launched two years ago by former U.S. Energy Secretary Steven Chu.
It did not directly analyse or comment on whether natural gas could play the role of a transition fuel.
But the results support the idea that natgas can work as a bridge between high-carbon coal and cheap solar power in areas with abundant sunshine, as policymakers build up renewable energy capacity and supporting infrastructure while driving deep cuts in carbon emissions.
There are two important caveats, however, to such a conclusion.
First, scientists have yet to agree to what extent shale gas production emits the powerful greenhouse gas methane, which may add to the carbon emissions from burning the fossil fuel.
Second, new gas-fired power plants have a lifespan running for decades, risking a long-term “lock-in” of fossil fuel use.
Chu’s initiative aimed to boost the competitiveness of the U.S. solar industry by supporting innovation, which has dragged down the cost of making solar panels.
It targeted a full installed cost of large-scale solar projects of $1 per watt by 2020, from about $4 in 2011.
It appears the solar industry is roughly on track.
The U.S. National Renewable Energy Laboratory collates voluntary cost data contributions from government, utilities, installers and the general public.
The “Open PV Project” records 238,037 solar projects with a total capacity of 5,525 megawatts, corresponding to 72 percent of installed U.S. capacity as of March 2013.
See link here: openpv.nrel.gov/
The database shows 681 projects larger than 1 megawatt, corresponding to the large-scale installations targeted by the sunshot initiative’s $1 goal.
Costs have roughly halved since the first of these projects, to below $3 per watt now from more than $6 in 2003, and appear roughly on course to meet $1 in 2020. (See Chart 1)
Chart 1: link.reuters.com/wav52v
Chart 2: link.reuters.com/bev52v
The second assumption in the University of California study, published last month, was a carbon emissions cut of 80 percent by 2050, consistent with limiting global warming to no more than 2 degrees Celsius.
U.S. action to cap greenhouse gases has seen little federal momentum lately.
Nevertheless, California has enacted regulation aimed at achieving an 80 percent cut (from 1990 emissions levels), while the present administration aspires to a national 83 percent cut (on 2005 levels), both by 2050.
The study focused on the Western Electricity Coordinating Council as an area with strong solar resources; the interconnected region includes western U.S. states, Canadian provinces and northern Mexico.
It assumed that solar costs remained at $1 after meeting the sunshot target in 2020; it used U.S. Energy Information Administration projections for gas and coal prices and power demand growth.
The study’s grid dispatch model selected power generating technologies that met the 2050 carbon emissions target at least cost.
It found that natural gas and solar power displaced coal in the near term, while cheap solar also delayed the development of other low-carbon technologies, including carbon capture, geothermal and wind.
Gas was the dominant power source for the next two decades.
Solar increasingly edged out gas from 2030, as deeper emissions curbs kicked in, becoming the main power source by the middle of the century. (Chart 2)
The study projected rising generation costs and a large build-out of transmission capacity.
There are two important caveats to the idea that natural gas can be a bridge to a decarbonised grid around 2050.
First, scientists are not agreed on the contribution of natural gas, and in particular shale gas, towards methane emissions.
Researchers differ on the amount of methane vented during the “flow-back” period between initial fracking and production at a shale gas well.
At one end of the spectrum, Cornell University researchers rejected a bridge role for shale gas on the basis that its total lifecycle greenhouse gas emissions could exceed coal.
A Massachusetts Institute of Technology study steered a middle ground - that fugitive methane was a concern but did not make shale gas substantially more polluting than conventional gas production, after taking into account best practice.
The second concern is that building long-lived gas-fired power plants will lock in the use of fossil fuels through 2050.
The International Energy Agency estimated in 2011 that as a result of lock-in, no new, unabated fossil fuel power plants can be built anywhere and stay within 2 degrees Celsius warming.
It took a rather conservative view, that all power plants would operate at their initial potential, whereas the example of Germany shows that higher levels of wind and solar power force gas plants to reduce output.
It also assumed that natural gas would not force the early retirement of coal, contrary to evidence in the United States.
The recent Berkeley study did not take explicit account of either fugitive methane emissions or the risk of fossil fuel lock-in.
The next research step would be to run similar economic, grid dispatch analysis taking account of these.
This is a notable research gap, given the public noise over the climate dangers, or not, from a “dash for gas”. (Editing by Dale Hudson)