Solar and hydro are often viewed as direct substitutes when discussing renewable energy sources. In Washington state, it is more accurate to view these renewable energy sources as competitors complements. “Hydroelectricity’s low cost, near-zero emissions, and ability to be dispatched quickly to meet peak electricity demand have made it one of the most valuable renewable energy sources worldwide.” However, a few of solar’s attributes can strengthen Washington’s grid in ways which hydropower simply cannot. The open question is how solar’s attributes should be valued (monetized) by society and by policy makers when determining how to replace coal and other high-emitting fuel sources. Data on the performance of existing installed PV as well as  modeling on solar supply is vital before crafting any new policies that pit solar against hydropower. This report provides only a brief starting point for further investigations.

Baseload and Peak Generating Capacity

Solar power is seasonal and unpredictable in Washington, given the state’s maritime climate and topography. Without energy storage, solar cannot compete with hydropower as a baseload electricity source, regardless of installed capacity. If additional capacity is installed, solar could provide utilities with a potential source of peak electricity in the early summer. As it happens however, those months coincide with spring run-off and peak hydroelectricity generation. June and July provide the most solar radiation in Washington. When supply exceeds demand, utilities face negative prices and hydroelectricity is exported out of state. Solar’s value proposition in that context is lost.

There are publications already on how to best integrate solar into the grid, and more are called for. The NW Power and Conservation Council (NWPCC) provides excellent tools and models PV generation, aka “supply,” resources. Those regional analyses are excellent starting points. However, solar’s intermittency and peak generation cycles pose unique and valid challenges to Washington’s hydro-dominant market. A detailed Washington-specific solar forecasting model would better inform if and how solar will add scaled value to the grid.

Carbon Emissions

Hydro is undeniably cleaner than solar in this regard. It should be noted however, that most of the lifecycle analyses of renewables are at least two years old, throwing some doubt on the accuracy of results for today’s strategy and policy making. We do know that Washington’s hydropower assets provide the economy with a significant source of carbon-free energy. With 2.2% of the U.S. population living in Washington, the state’s total carbon dioxide emissions are just 1.3% (2014 DOE Washington State Energy Profile).

PV modules’ lifecycle carbon emission rates have fallen each year as technologies improved: the latest panels have extended efficiency rates, longer estimated lifetimes, are made increasingly with recycled materials, and create fewer chemical pollutants during manufacturing. It is therefore important to continue updating carbon emissions models with updated performance data.  

Per Watt Cost

It’s close. Currently hydropower is less expensive on a per-watt, generation and consumption basis. NREL estimated “the levelized cost of incremental hydropower at existing dams to be $0.01 to $0.10 per kilowatt-hour (kWh) and the levelized cost of new small and micro hydropower to be between $0.06 and $0.14 per kWh.” Levelized solar currently costs $0.20/kWh. In five years, assuming further technological advances and holding constant current public policies, solar may be cost competitive with new hydropower plants.

Expansion Opportunities – Given the state’s existing hydropower plants, new hydro capacity will have to come in the form of small plants and/or additions and upgrades to existing assets. According to the NWPCC, seven such hydro projects are in the planning or proposal stages in Washington. The potential additional capacity is 49.8 MWa, hours of average MW energy. In contrast to restrictions that make siting a new hydropower facility a lengthy and complicated process, new sites abound for PV installations in Washington – be it utility scale, residential, or commercial. Given the current policy incentives as well as technological limitations, rooftop solar adoption is increasing at an ever-accelerating pace while other sectors are adopting at much slower rates.  

Grid Resilience – Hydropower is greatly affected by natural disasters and climate change, whereas distributed solar offers the grid protections against those same events. Decreased snowpack and changes to water melting and flow patterns uniquely affect hydropower capacity and forecasting. According to the EIA, “Precipitation for the hydrological year that began last October has been below 70% of normal levels throughout most of the Northwest.”

The Bonneville Power Administration 2014 Annual Report adds additional detail on how water levels and flow will affect planning. “Recent studies, including the latest information from the Intergovernmental Panel on Climate Change, agree that Columbia River Basin climate is likely to continue to warm. It is reasonable to expect that warming will cause more winter precipitation to fall as rain rather than snow, resulting in increased river flows in winter and early spring, reduced flows in summer and new challenges for river operations and planning.”

Though wildfires are predicted each year in Washington, 2014 and 2015 saw record scope and levels of fire-related destruction. As one example, the 2014 Carlton Complex fire destroyed a major transmission line in the Okanogan PUD service area, leaving nearly 3,600 consumers without power for eight days. The 2015 wildfires destroyed multiple transmission lines and caused power outages as well. In an unfortunate turn, smoke from the wildfires caused additional power problems. According to Seattle City Light, three dams on the Skagit River were shut down temporarily because “It was so thick that the particles in air were conducting electricity.” Lastly, Seattle’s 2015 summer windstorm took out power for over 300,000 consumers.

To be fair, disasters such as wildfires, landslides, and earthquakes would have the same impact on all types of centralized electricity distribution, be it utility-scale solar or hydropower. Since Washington’s solar capacity currently is 90% residential, and distributed across a wide geographic base, centralized hydro- and other electricity sources are much more vulnerable to natural disasters. Snowpack levels and precipitation timing do not pose the same challenges for centralized or distributed solar. If policy makers could fairly monetize the value of grid diversity – as a means of increased resilience against natural events – then non-hydropower renewables could be seen as increasingly cost competitive.

 This is part of a blog series in five parts.