The Obama Administration's recently proposed Clean Power Plan envisions renewable energy technologies such as biomass, geothermal, hydropower, solar, and wind providing 28% of U.S. power generation in 2030. Is that realistic? Pie-in-the-sky? Unduly conservative?

 

The answer might be found in both an analysis of recent trends, and in the dozens of technology-by-technology forecasts issued in recent years.

 

While the past is not necessarily prologue, historic growth patterns may provide a partial answer to what the future holds for the contribution by each of the major renewable energy technologies to the nation's electricity generating mix.

 

The U.S. Energy Information Administration (EIA) has been compiling and publishing energy statistics for the past four decades. Its most recent "Electric Power Monthly" report, released on July 27, 2015, presents detailed data for the period January 1, 2005 - May 31, 2015. In addition, the Federal Energy Regulatory Commission (FERC) has been issuing a monthly "Energy Infrastructure Update" since December 2010, with the latest edition published on July 21, 2015 with data through June 30, 2015.

 

The latter reveals the total installed operating generating capacity for all renewable energy sources has steadily increased over the past five years; from 13.71% in 2010 to 17.27% in 2015. Should that pace continue, renewable sources would account for about 28% of generating capacity in 2030.

 

Similarly, EIA data shows net generation from renewable sources accounted for 14.52% of the nation's total as of May 2015, nearly two-thirds higher than their contribution of 8.82% in 2005. More impressively, non-hydro renewables have more than tripled from 2.15% of the nation's electrical production in 2005 to 7.53% in 2015. Continuing to grow at that pace would bring non-hydro renewables up to almost 16% of U.S. electrical generation in 2030. With an additional 7% from hydropower, renewables would be at roughly 23% in 2030.

 

However, it should be stressed that EIA's data is incomplete because it fails to reflect much of the distributed renewable energy electrical supply that is not grid-connected. The Solar Energy Industries Association reports that distributed photovoltaics account for about 45% of total solar capacity; most of which is not reflected in EIA's data. While not similarly tabulated, distributed electricity from biomass, mini-hydro, small wind, and perhaps some geothermal sources is also missing from EIA's analyses. Thus, a reasonable guesstimate of renewable energy's actual share of net U.S. electrical generation today may be closer to 16%, and a projection for all renewables at current growth rates, might be 25% by 2030.

 

As the following analysis shows, however, making projections based on the growth pattern of all renewable energy sources combined fails to account for the differing growth rates of individual technologies, notably wind and solar. And it appears the U.S. EPA has forecast and set its renewable energy goals for 2030 on that basis.

 

Hydropower, as of May 2015, accounts for a bit less than half of the net electrical generation from grid-connected renewable energy sources, 7% of the 14.5%. Actual generation from hydropower has stayed largely unchanged over the past decade with electrical production in 2015 only 1.5% higher than in 2005 and installed capacity just 1.0% more in 2015 than in 2010.

 

There is significant potential for powering up existing non-power dams, as well as upgrading those in operation and to expand electrical production from water power via emerging hydrokinetic technologies (e.g., tidal, wave, currents). Whether that will increase hydropower's share of the nation's electrical mix by 2030 is speculative. Therefore, for the sake of this analysis, it is assumed hydropower will continue to grow at a slow pace, and remain approximately 7% of the electrical mix in 2030.

 

Of the five major renewable energy sources, geothermal is presently the smallest, accounting for less than one-half percent of the net U.S. electrical generation in 2015. Nonetheless, installed geothermal capacity has grown by 18.5% in the past five years and actual electrical generation is about 15% higher than a decade ago. Sites such as the Salton Sea offer potential for significant domestic geothermal growth, as do emerging technological developments such as Enhanced Geothermal Systems (EGS). However, for the moment, it will be assumed that geothermal will continue to expand at modest growth rates for the near future and likely contribute about 1% of the nation's electrical mix in 2030.

 

Biomass, defined by EIA to include wood and wood waste, municipal solid waste (MSW), and landfill gas, now accounts for 1.6% of the nation's net electrical generation. Over the past five years, installed biomass generating capacity has grown by over 23% but actual generation has increased by about only 9%. Prospects for future growth are uncertain, though, because there has been very little expansion of electrical generation from either wood, wood waste, or MSW.

 

Most of the recent growth in biomass has been from landfill gas, which has more than doubled its contribution to net electrical generation in the past decade. Nonetheless, landfill gas accounts for only a quarter of one percent of the total electrical generation in 2015. Assuming continued expansion of landfill gas at recent historic rates and modest growth rates for other sources of biomass, electrical generation from these sources combined in 2030 might be about 2% of the total.

 

This, possibly conservative assessment, suggests by 2030, hydropower, geothermal, and biomass combined might account for 10% of the nation's net electrical generation, leaving it up to solar and wind to provide the other 18% in EPA's Clean Power Plan goal of 28% renewables by 2030.

 

According to EIA data, during the first five months of 2015, wind and solar accounted for 4.92% and 0.63% respectively of the nation's net electrical generation. However, inasmuch as distributed PV may boost solar's real contribution by about 50%, and that some amount of small wind is not included, the combined actual share of the nation's electrical generation from wind and solar today is probably about 6%.

 

Thus, the question, and challenge, is whether or not solar and wind can triple their combined contribution over the next 15 years.

 

In the past five years, installed grid-connected wind generating capacity has almost doubled from 38.50 GW to 67.82 GW, while that of solar has increased eleven-fold, from 1.12 GW to 12.49 GW. Increases in actual generation since 2010 have been even greater with wind more than doubling its output by 2015 and solar 20-times higher.

 

Over the past decade, wind generation has grown from 17,811 GWh in 2005 to a projected 193,000 GWh in 2015, a greater-than ten-fold increase, while solar thermal and PV combined have gone from 551 GWh to a projected 24,624 GWh during the same time period. Grid-connected solar PV alone has roughly doubled its output every year since 2007. In fact, it has ballooned from 16 GWh in 2005 to a projected 21,670 GWh in 2015, a level over 1,000 times higher than a decade earlier. (2015 "projections" use EIA's figures for the first five months and multiply them by 12/5).

 

It’s not physically possible to sustain the annual percentage increases experienced by wind and solar over the past decade through 2030 but the incremental growth in actual electrical generation from both seems likely to continue. Since 2007, wind energy output has grown by roughly 20,000 GWh each year. At that rate, wind could be contributing nearly 500,000 GWh to the nation's electrical mix, or roughly 12%, by 2030.

 

If wind (12%), combined with hydropower (7%), biomass (2%), and geothermal (1%) were to provide 22% of net U.S. electrical generation by 2030, then solar would need to supply the remaining 6% to hit the U.S. EPA's target of 28% renewables. And that seems quite doable.

 

Again, grid-connected and distributed solar combined now account for about 0.6% and 0.3% respectively of the nation's electrical generation with actual generation roughly doubling for PV every year since 2007. Beyond the 2,500 GWh from solar thermal, grid-connected PV seems likely to grow from 15,874 GWh in 2014 to about 21,670 in 2015; distributed PV could increase PV's 2015 total by another 50%, an additional 2,900 GWh.

 

If future annual solar growth merely equaled that projected for this year, by 2030, solar electrical generation would total about 163,000 GWh or 4% of the nation's total.

 

That estimate, though, would seem to be ridiculously low in light of the still sky-high percentage growth rates for solar, and the rapid and continuing drop in prices for solar as well as wind, coupled with comparable cost declines for solar storage and advances in PV conversion efficiencies. Taking those factors into consideration, reaching 6% electrical generation from solar by 2030 seems within relatively easy reach.

 

For each of the major renewable energy technologies, there are recent analyses suggesting their future contributions could be significantly greater than previously indicated.

  

**A 2014 U.S. Department of Energy resource assessment estimated over 65 GW of potential new hydropower development cross more than three million U.S. rivers and streams - equivalent to the current U.S. hydropower capacity.

 

**A newly-released draft vision document from the Imperial Irrigation District Board of Directors sets a goal of 1,700 MW of new geothermal by 2030; the current installed capacity of geothermal power in the U.S. is around 3,900 MW.

 

**According to the National Renewable Energy Laboratory, the methane potential from landfill material, animal manure, wastewater, and industrial, institutional, and commercial organic waste in the U.S. is estimated at about 429 billion cubic feet - an amount that could displace about 5% of current natural gas consumption in the electric power sector.

 

**Citing EIA data, the American Wind Energy Association says that wind could provide “57% of the optimal energy mix to comply with the Clean Power Plan”, while a December 2014 report from Environment America notes that if wind power kept its recent pace of development, if could supply 30% of the nation's electricity needs by 2030.

 

**Last year, Bloomberg New Energy Finance forecast a 13-fold increase in global small-scale PV by 2030 while a 2014 study by Environment America suggested that 10% solar was reachable in the U.S. within two decades.

 

**In January 2015, a new report from the International Renewable Energy Agency said the U.S. could increase its use of renewable energy in power generation from 14% to almost 50% by 2030.

 

Obviously, these more optimistic forecasts are subject to numerous variables. The possible demise of the federal ITC for solar and the production tax credit for wind could greatly dampen prospects for both technologies, at least for a year or two, as could incoming political leadership on either the national or state levels, and/or by the electric utility industry.

 

On the other hand, rapidly dropping prices for all renewables - especially wind, solar, and storage - means that these technologies are now already cost-competitive in many spot markets and could very likely reach and exceed parity with fossil fuels, and certainly nuclear power, nationwide within the next five years. The renewable portfolio standards now in effect in 29 states will continue to drive renewable energy growth. And concerns about climate change and other environmental issues will prompt many communities, businesses, institutions, and individuals to invest in renewables, with or without formal government support.  

 

In sum, is the U.S. EPA Clean Power Plan's target of 28% electrical generation from renewable sources by 2030 realistic? The answer is probably yes with one possible mix being: wind - 12%, hydropower - 7%, solar - 6%, biomass - 2%, and geothermal - 1%.

 

And there is good reason to argue that EPA's 28% renewable energy target is unreasonably low and could well be reached sooner than 2030 and greatly surpassed by that date.

 

Ken Bossong is the executive director of the SUN DAY Campaign.