Integrated Renewable Energy for Communities

(The following article by Gerry Braun was published on September 1, 2015 in Renewable Energy World.  It included content from the executive summary of an IRESN report entitled Integrated Energy Analysis for Davis, California.  Click here for the Renewable Energy World article and here for a pdf of the full report.)

Toward a Template for Local Integrated Energy Analysis

                Thanks to cost-effective rooftop solar electricity, new neighborhoods in California are generating their own electricity from the start.  Likewise, local grids serving settled communities are being strengthened by deployment of local sources, smarter end use, and electricity storage.  Regulators are considering new grid architectures that allow each local grid to be operated according to its unique blend of local and imported supply and evolving usage patterns.

                In California, renewable energy deployment is gaining traction in support of locally established climate action goals.  Where such goals apply, electricity must, sooner than later, be substituted for natural gas use in buildings and for petroleum products in transportation, and new transportation fuels like hydrogen must be produced from local renewable sources.  Accounting for and tracking these changes will require timely and accurate integrated local energy analysis.   

                 In 2008, the California Energy Commission launched an R&D program to share the cost of related local planning and innovation with California communities.  To date 21 projects have been completed at a shared cost of more than $40 million, and the program’s next phase is in preparation.  The City of Davis, California recently completed one of the 21 projects.  The DavisFREE project proved the need for integrated local energy analysis and funded the development of analysis models that can be adapted to the needs of other communities.

                Some highlights follow that illustrate the data and assumptions cities and counties will need to use in evaluating their opportunities for climate action, choosing their energy service options and engaging collaboratively with local energy service providers.

                In general, Davis’ electricity service options include:  1) regulated for-profit utility service (current),  2) establishing a municipal utility, or 3) joining/creating a community choice energy agency.  Can Davis achieve its environmental and economic goals within the current framework of state regulated energy services?  Do alternative frameworks enable faster progress and more effective use of local resources?

                Energy usage, local energy supply and the supply/usage balance were modeled for the three above-mentioned electricity service options.  Scenario-specific models were developed to account for building and transportation energy usage and local solar, wind and clean vehicle deployment over the 20 year period from 2015 to 2035.

                Scenarios allowing high rates of local renewable deployment resulted in monthly and daily usage and supply variability that must be managed locally.  So, in these scenarios it was also important to determine amounts and timing of electricity imports and/or exports.

                In the past decade, Davis’s energy use has continued to inch upward in spite of intentionally slow population growth and statewide programs to encourage energy efficiency.  Its building energy use accounts for 72% of direct energy costs and carbon emissions.  Light vehicle energy use, accounts for 28%.  Transportation accounts for 50% of its carbon footprint when indirect heavy vehicle use is included.  Clean energy vehicle energy use is taking off and is expected to increase rapidly, adding significantly to local electricity usage.

                California’s long term energy strategy emphasizes efficiency and renewable energy.  These elements are necessary but not sufficient to achieve faster local than statewide carbon footprint reductions.  A third essential emphasis is substitution of low carbon for high carbon end use energy commodities. 

                For example, a major portion of Davis’s building energy is used to generate heat using natural gas.  Substitution would mean heating buildings with heat pumps powered by renewable electricity and heating  water with solar energy.  In the transportation sector, substitution would mean powering vehicles with renewable electricity, hydrogen or bio-methane, thus taking large bites out of Davis’s greenhouse gas emissions.

                Historically, almost all of Davis’s electricity has been “imported”, i.e. not produced locally.  (Energy in, dollars out.)  Now, however, Davis is blessed with cost-effective opportunities to generate solar electricity locally.  Also, there are good to excellent quality wind resources within 10 to 50 miles of Davis’ city limits.

                Solar water heating and bio-fuels are potential complements to solar and wind electricity, as is vehicle to grid electricity storage.  As fuel cell electric vehicles (FCEVs) gain a foothold, solar electricity, along with natural gas, will be used to produce hydrogen for the FCEVS.  In the longer term, additional hydrogen can be produced and used to displace natural gas for heating purposes and/or to fuel zero carbon residential and commercial CHP systems.  

                On-site solar electricity installations, preferably sized to at least match and preferably exceed on-site use, offer a simple and environmentally ideal pathway for increased dependence on local renewable resources.  At current per capita deployment rates five times the California average, on-site solar electricity would supply 20% of Davis’s electricity even without city engagement in energy planning and programs.

                 The potential for on-site solar PV to supply a large amount, or even the majority of the city’s energy needs is real.  At present this potential is forestalled by interconnection rules that severely impede on-site and local deployment.  Faster adoption of on-site solar would create a need to deploy cost-effective energy storage technologies.  Fortunately, the rate of battery powered electric vehicle adoption in Davis is mirroring the historical high rates of early stage on-site solar deployment.

                Many electricity users lack suitable space for on-site generation.  To enable their access to solar electricity, community controlled “brownfield” sites are available for larger (but still local) projects as a complement to on-site net positive power. However, in California  such “community” solar and wind projects are still impeded by surcharges, regulations and market rules that also preclude designation of locally generated electricity for local use.

                California legislation enabling “community choice energy (CCE) ”, i.e. local responsibility for sourcing grid electricity, provides a pathway for California cities and counties to avoid some current impediments and accelerate adoption of on-site solar and community solar and wind.  Cities served by publicly owned utilities (POUs) have even greater flexibility to accelerate adoption, while cities served by investor owned utilities (IOUs) have much less.


                How much difference could locally accountable electricity sourcing or service make for Davis?  Figure 1 shows an ideal build-out of local clean energy resources that could be implemented by Davis over the next twenty years according to the modeling assumptions for the POU scenario.

Figure 1.  Ideal Build-out of Clean Energy Resources for Davis

Click here for Figure 1.

Figure 2 shows combined decarbonization effects in the three scenarios of:  1) local renewable electricity build-out, 2) substitution of electricity for fossil fuels in heating and transportation sectors, and 3) locally effective energy efficiency and conservation programs. 

Figure 2.  Decarbonization Effects of Local Action in Three Scenarios    


               The above-mentioned report also provides results of quantitative modeling of locally implemented strategies to balance local supply and usage variability in scenarios that achieve both carbon neutrality and local self-reliance. 

                Analysis of production to balance monthly demand in the 20th year of the Davis case indicates that in summer months, some renewable electricity would be available for export or sale, while in winter months equivalent amounts of flexible local natural gas fueled electricity production would be needed to round out monthly supply.

                Analysis of hourly variations in daily usage indicated that seasonally varying  amounts of distributed electricity storage would be required to match daily renewable production according to demand over 24 hours of usage.

                Would  the likely amount storage embedded in locally based electric and plug-in vehicles suffice as a load shifting tool?  (For example, charging could be encouraged during hours when variable renewable supply exceeds building usage.)  Our analysis showed that it would not, per se.  So, plug-in vehicles can have a prominent role in supply/demand balancing, but other load management strategies will be needed as well.  

                Would projected cumulative vehicular storage capacity suffice to store excess generation during some hours and return it to the local grid when needed each day?  Our analysis showed that it would in most but not all months.  So, some additional stationary storage might be required.

                By implementing a locally integrated energy supply plan and taking full economic advantage of local renewable resource opportunities, Davis and many other cities blessed with abundant high quality local renewable sources can achieve a near zero carbon local carbon footprint by 2035 while reducing electricity supply costs.  Integrated local energy analysis is key to the economic and environmental benefits of planning and developing local renewable supply.   

                Locally accountable energy service may prove essential to effective integrated energy planning and deployment.  A dozen or so northern California cities are already served by municipal utilities.  A couple dozen more are already taking responsibility for electricity sourcing under California’s community choice aggregation law.

                As a result, these communities will have relatively convenient and unfettered access to data necessary for definitive integrated local energy analysis.  Others simply evaluating their options will not and may need to rely on preliminary scoping methods as described above and in more detail in the report entitled Integrated Energy Analysis for Davis, California