Almost everyone has a story about receiving an awesome gift, only to find they couldn’t use it until hours later because the box lacked one essential item — the battery. Remember the frustration, and how easily that manufacturer could have made you happy if they weren’t so cheap?
You may be equally annoyed to learn that well-intentioned codes and green building certifications, with the exception of Passive House, have been doing exactly the same as these manufacturers — omitting an essential operational item from their packaging and short-changing building owners, many of whom intended to be significant contributors to addressing climate change.
How is this possible?
The skewed economics of net metering
In the rush to accelerate and incentivize the installation of PV systems, well-meaning governments and utilities set up net metering1 or feed-in tariff pricing structures whereby building owners are paid for all the energy they supply to the grid (generally at the utility wholesale price and sometimes at full retail price) regardless of when the energy is generated and whether there is a demand for it. This worked well — until it didn’t. When excess summer generation started to wreak havoc on grid pricing structures, the flaw in net metering could no longer be ignored and utilities were still required to supply peak loads when renewable energy generation couldn’t match demand.
Utilities2 started to push back against these newly empowered (pun intended) home energy generators, who now had access to their own means of production (but not distribution.) These new grid contributors failed to recognize that their energy was not being saved for use at a more convenient time — the grid is not a storage system and is not set up to provide banking services. Yet they still felt entitled to be paid, regardless of whether their energy was being used or not.
This issue of electricity demands that are misaligned with solar contributions hit the early adopter regions of Germany first, followed by the states of Hawaii and California, where it has set off the biggest duck-related crisis since California’s 2004 attempt to ban foie gras3. Many a power-point pundit prematurely clanged the death-knell of the utility business model, as they simultaneously scratched their collective heads on how to flatten the “duck curve”4 — the name given to the graph illustrating the exacerbated ramp-up of daily peak demand caused by the incongruous timing of increased solar generation. Clearly, renewables alone were not going to meet our daily energy demand cycles or relieve utilities of the burden of meeting peak loads — which still commonly must be met using fossil fuel sources.
Which peaks matter?
To make matters worse, well-intentioned policymakers, code developers, and building certification entities may have inadvertently exacerbated this misalignment by pushing building programs optimized by net-metering economics, which rest on the flawed assumption that the grid functions as a bank. This assumption increases the difficulty of meeting winter peak loads.
We must first acknowledge that there are actually two peaks in building energy use: daily and seasonal. The duck curve reflects the daily peak cycle, but the more challenging peak happens as we move from cooling to heating loads. Because net-metering economics distribute PV generation over the year, rather than seasonally, this seasonal peak is discounted, as are the benefits of increased efficiency measures. Efficiency improvements become disproportionally skewed by the decreasing costs of generation and are made to look less cost-effective. Insulation levels become determined by annual average building performance, rather than by seasonal requirements. (This is the equivalent of advising someone to wear the same outfit all year round, instead of dressing according to the season.) Building programs — including many aiming at net zero — may have missed the opportunity to optimize performance for worst-case, seasonal loads, which in turn makes a transition to all renewable energy generation that much more difficult.
The arc of efficiency
One of the few building standard frameworks that has not fallen into this net metering trap is that developed by the Passive House Institute (PHI). When PHI overhauled their source energy targets in 2015 to include an equitable accounting for renewable energy, both short- and long-term battery storage were carefully considered. Efficiency measures were kept isolated from solar generation credits, while the need for electrical storage was factored into, planned for and optimized for the future scenario of an all renewable energy. As a confirmation of this methodology, a 2016 study conducted by Delia D’Agostino of the Joint Research Center, European Commission and Danny Parker of the Florida Solar Energy Center modeled a baseline building in various climates across Europe to find the most cost-effective options for reaching the European Union’s nearly Zero Energy Building (nZEB) targets. Both U.S. and European researchers confirmed “that it is possible to reach a very low energy design in new buildings with source energy savings approximately between 90% and 100% or beyond.”5 Their study affirmed the need to include costs for short-term electrical storage as part of a more accurate economic assessment.
We now know that commercial-scale battery storage combined with solar — a combination that helped address peak loads in Kauai6 —can easily “confit” the duck curve of our daily peak loads. Further innovations in short-term battery storage will quickly (and likely economically) solve our daily peak challenge. However, in order to fully wean ourselves off fossil fuels, we will need to shift our building frameworks to mirror those of Passive House standards, which focus specifically on reducing peak demands in order to shave peak seasonal loads. To do so, the cost of storage must be included in all optimization calculations in order to economically transition to an all-renewable-energy future.
Factoring in storage
The new Primary Energy Renewable (PER) factors utilized by the Classic, Plus, and Premium Passive House standards include a localized assessment of requirements for short- and long-term storage. These naturally differ by climate and are a function of renewable energy supply over on-site seasonal demand. As we can see from the graphs shown in Image #2 (below), short-term battery storage is only fully effective in the summer, when these batteries can be regularly recharged. However, the winter month of January shows long periods where these batteries are not replenished and supplemental grid power is required. These periods will require innovation in long-term renewable energy storage technologies in order for our grid to become truly fossil-fuel free.
The race for renewable energy storage currently looks like a competition between two gasses: the conversion of renewable energy into either hydrogen or methane, both of which can be burned cleanly and (hopefully) safely at the power plant. Whichever gas wins, it’s clear that we will need to bend the arc of energy efficiency to drastically reduce peak winter demands in order to transition to an all renewable energy future. This is exactly what Passive House already does.
Passive + Renewables is the focus of the upcoming 2017 North American Passive House Network Conference & Expo, being hosted in Oakland from October 4th to 8th, 2017. The Primary Energy Renewables framework will be more deeply explored at this event in workshops and presentations during the core conference program.
This article was originally written for Passive House Buildings, the magazine of the North American Passive House industry, which is published by Low Carbon Productions.
1. Net metering (or net energy metering, NEM) allows consumers who generate some or all of their own electricity to use that electricity anytime, instead of when it is generated.
3. The California foie gras law, California S.B. 1520, is a California State statute that prohibits the “force feed[ing of] a bird for the purpose of enlarging the bird’s liver beyond normal size” (California Health and Safety Code § 25981) as well as the sale of products that are a result of this process (§ 25982).
4. In commercial-scale electricity generation, the duck curve is a graph of power production over the course of a day that shows the timing imbalance between peak demand and renewable energy production.
5. Comprehensive Modeling of Optimal Paths to Reach Nearly Zero Energy Buildings (nZEBs) for New Constructions in Europe by Delia D’Agostino and Danny Parker.
Bronwyn Barry is an architect and the president of the North American Passive House Network (NAPHN.)