6. Metrics and Boundaries: What Exactly Is a Zero Net Energy Building?

Solar Market Pathways, “Virtual Net-Metering Policy Background and Tariff Summary Report,” June 30, 2015.

See: COMNET.org, http://​www.​comnet.​org/​mgp/​content/​appendices?​purpose=​0.

The California Energy Commission requires that their standards be cost-effective, but at the same time the standards encourage the use of natural gas for water heating and space heating. This creates a cost-effectiveness challenge, since current utility tariffs offer lower compensation for electricity exported in excess of electricity used, which is a requirement for ZNE buildings that use gas. There is less incentive to put in a larger PV system to make up for the gas use because the payback is reduced.

US Department of Energy, op. cit.

This is calculated using EIA data shown in figure 1-2, but the energy inputs from noncombustible renewable energy are adjusted to use the “captured energy” approach described in the United States DOE Request for Information DE-FOA-0001512, February 2, 2016. The 4.97 quads of non-combustible renewable energy shown in figure 1-2 are reduced to 1.78 quads by multiplying by the ratio of the captured energy (3,412 Btu of heat content) to the typical fossil-fuel plant heat rate of 9,542 Btu/kWh. The fossil-fuel plant heat rate was taken from the above-referenced report. Transmission and distribution losses are assumed to be 1.0 quad, which is consistent with recent estimates by EPA. The generation efficiency of 33 percent is calculated as follows: energy inputs = 38.0 – (4.97 – 1.78) = 34.81; energy delivered = 12.6 – 1.0 = 11.6; efficiency = 11.6 / 34.81 = 33 percent.

The question of source energy vs. site energy is by far the most contentious issue that is debated in the energy development arena at the national level. The associations representing the electric and gas industries have battled over this for years. The ASHRAE Standard 90.1 committee compromised on energy cost as its metric in 1989, and this has survived to this day.

See: http://​www.​presidency.​ucsb.​edu/​ws/​?​pid=​7842.

See: http://​energy.​gov/​articles/​top-9-things-you-didnt-know-about-americas-power-grid.

Selling energy back to the utility is often constrained. California investor-owned utilities, for instance, will buy what you produce at retail rates until you produce more than you use. They buy the remaining electricity at a discounted rate, closer to the wholesale rate.

Some of the negotiations were brutal. In the 1990s, a related issue emerged over a dual-­envelop standard, whereby the insulation requirements in the standard would be more stringent for buildings with more-expensive electric heat as opposed to buildings with gas heat or heat pumps. A number of environmentalists were dismissed from the project committee and new leadership was installed. The new leadership, in turn, was rejected by the IESNA, a co-sponsor of the standard.

LEED is the US Green Building Council’s Leadership in Energy and Environmental Design (LEED) program.

The areas served by the Tennessee Valley Authority (TVA) and the Bonneville Power Admin­istration (BPA) are cases where the price for electricity is held below market rate because of government investment.

The average electricity price used in standards development work is $0.1032/kWh ($0.03025/kBtu). The national average for natural gas is $0.99/therm ($0.0099/kBtu). These data are used in the Standard 90.1 development process.

For the actual TDV values used in California, see: https://​ethree.​com/​public_​projects/​2013_​title24.​php.

For more information, see: https://​ethree.​com/​National_​Time-Dependent_​Values.​html. EThree is the organization that developed the TDV values for California; at this site, you can download a spreadsheet that calculates TDV values for eight cities in the United States—Atlanta, Washington, New York, Phoenix, Fresno, St. Louis, Chicago, and Houston.

See: www.​COMNET.​org.

To verify that source energy and carbon track each other closely, compare the electricity­-to-gas ratio for both source energy and carbon. For CO₂e emissions, the ratio is 1.39 : 0.48, or 2.90. For source energy, the ratio is 3.15:1.09, or 2.89, almost the same. If you reduce energy by 50 percent, you also reduce CO₂e by 50 percent, even if the mix of fuels changes between the baseline and the efficient building.

CO₂e assesses all greenhouse gases in terms of the equivalent emissions of CO₂. It is based on their global-warming potential (GWP), which is an index for estimating the relative global-warming contribution of atmospheric emissions of 1 kg of a particular greenhouse gas compared to emissions of 1 kg of CO₂.

See the United States DOE Common Definition for Zero Energy Buildings, op. cit.

See: https://​us.​fsc.​org/​.

Meadows, op. cit.

Ibid.

See: http://​kids.​mongabay.​com/​elementary/​201.​html.

These calculations are based on 67 percent conversion efficiency and 20 million Btu/cord of wood. Another key assumption is that a cord of wood can be sustainably produced for each acre of land. This will, of course, vary significantly by climate and the type of wood that is grown.

This is based on 1,200 kWh/y of PV production per kW (STC) of installed capacity and 68 ft² of collector area per kW (STC).

Some boilers are designed to take multiple fuels. They can operate with wood pellets, or they can alternatively use oil or even natural gas.

The performance of solar water heating systems is commonly expressed in terms of an energy factor (EF), which is the ratio of the energy that goes into the process divided by the heat delivered by the system. The EF for a typical gas water heater is in the range of 0.70–0.80. The EF of a typical electric-resistance water heater is close to 1.00, but this does not account for power generation and distribution losses. Solar systems with gas backup have an EF in the range of 2.5, while solar systems with electric backup have an EF in the range of 3.3. The EF is calculated using site energy, so as you compare electric and gas water heaters; keep in mind that the energy costs and source-energy values will be higher for the electric systems. Solar-thermal systems are also sometimes rated in terms of a solar-savings fraction (SSF), which is the amount of the heating load that is provided by the solar system. A solar savings fraction of 60 percent means that 60 percent of the load will be satisfied by the solar system and the remaining 40 percent will be satisfied by the backup system.

See: http://​www.​foothill.​edu/​news/​newsfmt.​php?​sr=​2&​rec_​id=​3062.

The campus goals and plan is spelled out in some detail in the UC Merced Sustainability Strategic Plan (2010).

Solar Market Pathways, op. cit.

Shanti Pless and Paul Torcellini, “Net-Zero Energy Buildings: A Classification System Based on Renewable Energy Supply Options,” Technical Report NREL/TP-550-44586, June 2010.

See: http://​apps3.​eere.​energy.​gov/​greenpower/​markets/​certificates.​shtml?​page=​2.

Additionality is the property of an activity being additional; it is determined according to whether an intervention has an effect compared to a baseline.

See: https://​sustainable.​stanford.​edu/​campus-action/​stanford-energy-system-innovations-sesi.

For the PG&E tariff that applies in such an instance, see: http://​www.​pge.​com/​tariffs/​tm2/​pdf/​ELEC_​SCHEDS_​RES-BCT.​pdf. For a description of the program, see: http://​www.​pge.​com/​en/​b2b/​energytransmissi​onstorage/​newgenerator/​ab2466/​index.​page.

Information from e-mail correspondence with Joy Hughes and from her website, www.​SolarGardens.​org. See also: http://​www.​utilitydive.​com/​news/​why-utilities-across-the-nation-are-embracing-community-solar/​354164/​.

See: http://​blog.​solargardens.​org/​2011/​06/​guest-post-smud-solar-shares-in.​html.

J. R. DeShazo, Alex Turek, and Michael Samulon, “Guide to Design Decisions for Utility-­Sponsored Community Solar,” Luskin Center for Innovation, UCLA, May 2015.

See: http://​www.​greentechmedia.​com/​articles/​read/​us-community-solar-market-to-grow-fivefold-in-2015-top-500-mw-in-2020.

See: https://​www.​ftc.​gov/​sites/​default/​files/​documents/​federal_​register_​notices/​guides-use-environmental-marketing-claims-green-guides/​greenguidesfrn.​pdf.

The investor-owned utilities in California are allowed to use unbundled RECs to meet a maximum of 10 percent of their RPS commitment, but most use RECs for far less than this, partly because the California Air Resources Board (CARB) does not allow RECs at all and the utility will still have to buy carbon offsets to meet California’s cap-and-trade program on carbon.

According to Geof Syphers, the CEO of Sonoma Clean Power (SCP), a community-choice aggregator in California, there is not much demand for unbundled RECs. SCP will have none in its RPS portfolio after 2016, and Goef reports that the share of RECs in the PG&E RPS portfolio is around 1 percent, much lower than the 10 percent that is permitted.

One of the harshest critics of RECs is Auden Schendler, who has blogged about these issues in www.​thinkprogress.​org. See, for instance: http://​thinkprogress.​org/​climate/​2011/​06/​07/​238244/​clean-energy-trainwreck-why-most-recs-are-bad-and-how-to-find-the-good-ones/​.

During this period, the Roman Catholic Church would sell an indulgence that would absolve the purchaser from a sin that had been committed or even one that might be committed in the future. In 1517, Martin Luther denounced the Church for selling indulgences, and this was a factor in igniting the Protestant Reformation. See: Paul Vitello, “For Catholics, a Door to Absolution Is Reopened,” New York Times, February 9, 2009, http://​www.​nytimes.​com/​2009/​02/​10/​nyregion/​10indulgence.​html?​pagewanted=​all&​_​r=​0.

To achieve ZNE, a 10,000-square-foot building with an EUI of 12 kBtu/ft²·yr would require 120 million Btu/yr or 35 mWh of renewable energy production each year.

The estimated cost of the on-site PV system is based on a 30 kW system at a cost of $3/W.

The classic case of split incentives is that the owner is disinclined to invest in energy efficiency, since the benefits would accrue to the tenants who pay the utility bills.

See: http://​www.​green-e.​org/​.

Interview with Jennifer Martin, executive director of Green-e, January 13, 2016. See also: http://​www.​green-e.​org/​.

Severin Borenstein, “Feeling Smug about Your Solar Rooftop? Not So Fast” (blog posting), January 21, 2016, http://​blogs.​berkeley.​edu/​2016/​01/​21/​feeling-smug-about-your-solar-rooftop-not-so-fast/​.

See: http://​www.​cpuc.​ca.​gov/​PUC/​energy/​Renewables/​. Most states exclude large hydro plants from eligible renewable-energy generators, since they are legacy plants and it is unlikely that any large new hydro plants will be constructed, both because the best sites have been taken and because of environmental and land-use problems.

See: https://​www.​eia.​gov/​todayinenergy/​detail.​cfm?​id=​4850. See also: http://​www.​cpuc.​ca.​gov/​RPS_​Homepage/​.

The California RPS requirements define three different forms of renewable energy, which are called “buckets.” For an explanation of the California buckets, see: http://​www.​cpuc.​ca.​gov/​RPS_​Procurement_​Rules_​33/​. Most of the renewable energy must come from bucket one, which represents eligible renewable-energy systems that communicate directly with the California Independent System Operator (CaISO). The minimum amount in bucket one is 75 percent, beginning in 2017 (65 percent now). Bucket two includes renewable energy that may be substituted and “firmed and shaped.” Note the following example: An IOU buys wind energy from a farm in Oregon, but that energy is substituted or augmented with energy from conventional generators so that it does not have the variability inherent with wind. This substituted energy is what actually arrives at CaISO. The third bucket are unbundled RECs. These can represent a maximum of 10 percent after 2017 (15 percent now).

Lawrence Livermore National Laboratory, op. cit. Solar = 0.532, hydro = 2.39, wind = 1.82 and geothermal = 0.224. The total is 4.97 quads, or 13 percent of the 38.0 quads of input to electric generation. (See fig. 1-2.)

Ibid. For the state of Washington in 2012, 1,100 trillion Btu was used to generate electricity. Hydro represented 850 trillion Btu, with another 63 trillion Btu from wind. See: https://​flowcharts.​llnl.​gov/​content/​assets/​images/​charts/​Energy/​Energy_​2012_​United-States_​WA.​png.

See: http://​www.​midwestenergynew​s.​com/​2012/​01/​13/​renewable-or-not-how-states-count-hydropowe/​.

For Sonoma Clean Power, PG&E adds a PCIA/FF, which represents the power charge indifference adjustment (PCIA) and the franchise fee surcharge (FF). The PCIA is a charge to cover PG&E’s generation costs acquired prior to a customer’s switch to a third-party electricity-generation provider. PG&E acts as a collection agent for the franchise fee surcharge, which is levied by cities and counties for all customers. These charges add $0.01234 per kWh of cost.

See: https://​en.​wikipedia.​org/​wiki/​Community_​Choice_​Aggregation.

Conversation with Geof Syphers, CEO of Sonoma Clean Power, February 22, 2016.

Renewable Energy Self-Generation Bill Credit Transfer (RES-BCT). The capacity of the renewable-energy system is usually limited (less than 5 megawatts in California).