- Solar Decathlon Time Lapse
- FEMA & USGBC on Resilient Communities
- Blots, or Blotting
- Interactive Map of ARPA-E Projects
Zero Net Energy (ZNE) is a term that is increasingly heard throughout the architecture and building sector, but it is also a term that can mean different things to the different people who use it. In this series of posts I will give an overview of the four common definitions of ZNE, and a brief expansion on their respective implications in relation to policy structures and physical infrastructure.
The four common definitions of ZNE are: 1. Zero Net Site Energy, 2. Zero Net Source Energy, 3. Zero Net Energy Cost, and 4. Zero Net Energy Emissions. All four of these calculations are as measured over a calendar year, or on an annual basis. The difference is in the metric (the “thing” being measured) and the boundary (what is included in the calculation). All four definitions can be applied to –and calculated at– a “community” or multiple-building scale as well. In all cases the “net” part refers to how energy is accounted for at the grid level; low energy buildings that are not grid tied would therefore not be under a zero net energy designation.
Part 1. Zero Net Site Energy
what this is: A Zero Net Energy Building is one that uses no more energy than it can produce on-site within one calendar year (this is the most commonly used definition of the term “zero net energy” at present).
what this means: A “site” can be defined as either the building footprint itself or the building and the property it sits on. In this definition, the building/ building site would incorporate a form of on-site renewable energy such as solar (most common), wind, small hydro or biogas. As mentioned, a ZNE building is still tied to the larger energy grid. For example, a ZNE building that generates energy through the use of solar panels would create a surplus of power while the sun was shining (and the excess power would be fed back into the grid), but would have to draw power from the grid in the evening or during cloudy days. The goal here is for the overall power drawn within one calendar year to be less than or equal to the power generated.
pros, cons & considerations: The chief benefit of this definition is that it promotes deep efficiency at the single building scale. This is because in order to viably (and cost effectively) achieve this definition of ZNE, it is much more desirable to build the lowest energy-use building possible and then add a source or renewable generation. In addition, ZNE sets a concrete goal to achieve and thus can be a more useful target than trying to meet or best shifting baselines as building performance codes change.
However, buildings are built in many types and have many necessary functions- not all of which are compatible with the site definition of ZNE. For example, hospitals, restaurants, industrial activities, etc., may all have a very hard time achieving a ZNE facility because of unusually high energy demands. In addition, high-rise buildings and urban infill sites have their own challenges due to physical constraints (poor solar access, low rooftop-to-building ratio, proximity and density issues, etc.)
The implication here is that if a ZNE site-definition goal is in place on a policy level, at a certain point it becomes necessary to start looking at the issue from a multiple-building, or “community”scale, that would allow energy balancing between buildings to achieve an overall ZNE outcome (this is a simplification, but that is the main point).
P. Torcellini et al., Zero Energy Buildings: A Critical Look at the Definition, National Renewable Energy Lab, 2006.
Image: Wikimedia Commons
While attending a recent talk given by Paul Kephart, president of pioneering ecological design firm, Rana Creek, I heard an interesting assertion: Green roofs can improve the performance of solar photovoltaics by up to 30%. This would be due to the ability of the green roofs to lower the ambient temperature surrounding the panels, thereby boosting efficient operation.
Plants + solar PV may be an exciting possibility for synergistic systems on rooftops, especially in dry climates like California.
I have been looking around for studies or more information about this and came up with just a few articles that are linked below. Portland State University has a study underway on this topic.
On Tuesday, January 25, I was in the audience at the SPUR Urban Center in San Francisco as Panama Bartholomy, CEC, and Emma Wendt, PG&E, gave presentation about California’s clean energy future.
The post below consists of Part 3 of my record of the presentation – Emma Wendt’s presentation. All portions are included in chronological order.
An ellipsis (…) indicates that I was not able to capture the words or thoughts skipped. The presentation is transcribed as accurately as possible – punctuation choices are mine. I also added any photos or images.
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Most people don’t think of utilities as wanting to do something to address the clean energy future… You might know PG&E through your utility… We’re a really large but really green utility… We’ve won greenest utility in America for the last 2 years… We have a really green portfolio… We have a significant amount of solar interconnected into our system…
What do we mean when we talk about a sustainable electric system?… … The first step in cleaning up the system is to supply green power… On the customer side, you can add rooftop solar and plug-in electric vehicles. But because you have peaks in demand, and an intermittent demand… you need some sort of storage system to make sure demand can always be met by supply… Also need a way for all of this to talk to each other.
On the renewable side, there are a number of ways you can interconnect renewables into our grid… There are a number of programs – California Solar Initiative, Self-Generation Incentive Program, net energy metering, feed-in tariffs, and the renewable auction mechanism, which are hot of the policy presses…
We have a renewables RFO, where we look at the feasibility of projects … … and PG&E is looking at more options for owning renewables.
So why are we doing all this? … … We do have the renewable portfolio standard…
Another policy hot off the presses is the TREC decision – only allowed to buy out-of-state renewables for up to 25% of our renewables obligation… …
[Showing 2009 electric power mix.] This is what was actually delivered. We don’t yet have final 2010 numbers…
In the future, we have a ton of contracts for new renewable sources. A large part is solar – both solar thermal and solar PV… … You’ll only see a small amount coming from small hydro – basically the rivers that can be dammed are already dammed up… …
PV program hopes to speed up future PV installations… … if you are a developer of small-scale renewables projects, the RFO comes out next week… … On the utility side, we are planning to build more substations… … We want to build solar PV near our substations…
In reality, renewables projects in California don’t always get built. As of the end of 2009, half of our projects were cancelled or significantly delayed… … transmission is causing the most delays, but other barriers are significant – financing, developer inexperience… permitting, technology risks… site control, and the list goes on.. …
PG&E is involved in a statewide initiative called California’s Renewable Energy Transmission Initiative (RETI)… you can’t have clean generation without a way to get it to where the people are. This is a really big problem… …
PG&E customers lead in on-site solar generation… but the best resource is energy efficiency… … PG&E offers a wide range of customer energy efficiency programs… … we also have a program where we work on appliance standards… And we work with retailers… to give them the incentive, then they have control over what they put in front of their customers… …
A cool tool to help customers find out more about EE is also SmartMeters. You may have heard a number of things about SmartMeters… But there is the possibility of seeing what your load is like.
PG&E is also looking at options for plug-in electric vehicle integration… looking at meters for the charging of EVs, and having a separate pricing system… We have a number of partnerships with organizations working on electric vehicles.
We hope that we’ll have a really involved community to help this all move forward.
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This presentation was followed by a question and answer session with the audience.
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You can read our post on Greenwashing here.
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A number of start-up companies are trying to formulate a business model that sells hot water, lights, air conditioning, and solar power as a service.
The rationale is that the folks occupying buildings don’t necessarily want to own the equipment that produces hot water, light, cool air, or solar power, but they do want the end result.
The current model is that the companies (such as Skyline Innovations and Metrus Energy) retrofit commercial and industrial buildings, retain ownership of the equipment, and then charge a fee for the energy avoided. Because the fee is almost always less than the cost of the energy avoided, and because the maintenance costs of the equipment are generally included in the fee, the building owner can see further savings.
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I know what you’re thinking – a really exciting topic. But this question has actually come up in conversation a remarkable number of times in the last couple of weeks. This is not intended to be a definitive guide, but just to start the delineation between the organizations.
In a future post, I will discuss some of the practical ways that these organizations influence energy efficiency policy in California.
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Photo Credit: Wikimedia Commons
The CEC is California’s primary energy policy and planning agency.
The CPUC regulates privately owned electric, natural gas, telecommunications, water, railroad, rail transit, and passenger transportation companies.
This post will focus only on the energy aspects of the CPUC’s role.
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The California Energy Commission (CEC)
The five CEC commissioners are appointed by the California governor and must be approved by the Senate. Terms are five years. Commissioners must represent the following specific areas of expertise: law, environment, economics, science/engineering, and the public at large.
The CEC’s responsibilities include:
The CEC is located in Sacramento, CA.
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The California Public Utilities Commission (CPUC)
The five CPUC commissioners are also appointed by the California governor and must be approved by the Senate. Terms are six years.
The CPUC regulates investor owned utilities (IOUs) that distribute electricity and natural gas, including Pacific Gas & Electric Company (PG&E), Southern California Edison (SCE), San Diego Gas & Electric Company (SDG&E) and Southern California Gas Company.
The CPUC does not regulate municipal utilities, such as the Sacramento Municipal Utility District (SMUD).
The CPUC’s mission is the following:
The CPUC has a number of different divisions; the Energy Division assists Commission activities in the electricity, natural gas, steam, and petroleum pipeline industries. Energy Division handles the regulation and Commission approval of official rates and terms of service for energy IOUs.
Because the regulated California utilities are so large, and their programs reach so many customers, CPUC energy policy decisions and goals have wide influence in California. The CPUC touches programs in energy efficiency, demand response, low-income assistance, distributed generation, and self-generation, among others. It has a role in California climate policy. It is overseeing the CA utilities’ switch to Smart Grid technologies. The CPUC regulated electric generation and procurement, electric rates and markets, gas policy and rates, and electric transmission and distribution.
CPUC headquarters are in San Francisco, CA.
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