Case studies from San Diego County, Santa Monica, Sacramento County and Berkeley: How to best use innovative technologies to head towards Zero Net Energy
CURRENTS Summer 2016
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Local governments across California are exploring how they can lead the movement to zero net energy. At this year’s SEEC Forum, we asked California’s cities and counties to share with us how they are using innovative technologies to find deep energy savings in their buildings – and it turned out speakers were all using technology and design to push toward a zero net energy goal. We learned about a range of approaches across new construction and existing buildings, highly automated and controlled buildings and buildings where the architectural design is used to drive energy savings.
San Diego County’s new Alpine Library
Susan Freed from the County of San Diego shared the County’s experience with their first zero net energy new construction building: the Alpine Library. The County has committed to building zero net energy new construction wherever possible compelled by the fact that ZNE buildings are more affordable to operate and pay off in the long run – as well as the fact that reducing emissions and creating sustainable buildings supports the City’s Live Well initiative. The County’s analysis also shows that building ZNE new construction will get them 20% of the way to the state’s ZNE goals for 2030.
The County began exploring how to make their planned new library zero net energy in 2013. The County hired a firm to conduct a feasibility study, to provide them with findings they could use in their design-build RFP process. The budget for the library had been established prior to zero net energy planning, so additional funds were added for the cost of solar photovoltaics (PV), since that renewables were not expected to be covered by the original budget. The feasibility study included energy modeling estimates – the County used modeling throughout planning, RFP development and negotiation, design and construction, and is now using it for measurement and verification, and recommends: model early and model often.
The County’s Alpine Library was able to use many passive design techniques – such as southern exposure to maximize the use daylighting, and northern exposure for ventilation and cooling – to make the building’s layout and envelope as efficient as possible. In new construction buildings, passive technologies can be some of the most cost-effective – and don’t require the tuning or operational training that other technologies may require. The building’s insulation meets energy code but doesn’t go much beyond the code – while this had been an option considered, the energy modeling showed that other methods for achieving zero net energy were more cost-effective. The Library is also using high-efficiency LED lighting, high-efficiency performance glazing, variable refrigerant flow (VRF) with heat capture to heat and cool the building, as well as solar thermal hot water, and a building automation system with HVAC and lighting controls. The County decided to pursue ZNE certification through the Living Building Challenge and therefore chose to make the Library all electric (without onsite fossil fuel combustion).
The Alpine Library opened for business in May 2016. The County will continue to work with Library staff to measure and verify the energy use of the building. For more on the Alpine Library see this fact sheet.
SMUD’s East Campus Operations Center
From 2011 to 2014, the Sacramento Municipal Utility District (SMUD) worked to construct a new $122 million campus for their East Campus Operations Center, which required space to double in size. The goal was to use the opportunity of new construction to make the new 51-acre campus – including five stories of office space and control center, warehouses, and transportation facilities – LEED Platinum certified and zero net energy. As shared by SMUD Manager Jim Parks, the District found that zero net energy buildings sometimes don’t operate as had been intended – and has made a series of fixes to correct the campus’s energy use back toward its zero net energy goals.
Built using dirt infill on top of the site of an old gravel pit, the campus leverages geothermal technology for cooling (including pre-cooling of chiller plant water) using pipes 14 feet below the surface. HVAC needs are supplied by a central utility plant with chillers with heat recovery, air source heat pumps, and a radiant heating and cooling system using pipes laid in the office building ceilings. Lighting is high-efficiency LED technology with occupancy sensors, and utilizes daylighting. Plug loads are reduced through low wattage fans and computer and phone equipment. Renewable energy is supplied through 1.1 megawatts (MW) of single tracking solar photovoltaics (PV), and solar thermal hot water. A bioswale collects rainwater for greywater reuse, and conduit is laid for electric vehicle charging and expansion.
After the campus was completed and began operation, staff monitored energy use – and found that the campus was off from its zero net energy targets by over 40%. SMUD pulled together a team to examine what why energy use was so high and review what could be done, and found:
- Many of the sophisticated control systems were not working as expected. Much of the building’s energy efficiency is dependent on well-controlled management of lighting use (and intensity), plug load, and HVAC operations. It was found that daylighting controls were incorrectly bundled, and parts of the building were keeping their lighting and computer monitors on around the clock even though staff were gone for the day by 5pm. All in all, SMUD staff identified 102 different measures to improve and correct these issues
- The solar photovoltaic system was not generating as expected – this issue is in the process of being resolved.
- Additional fixes in the HVAC systems and central plant, plug load management are planned.
SMUD staff’s careful monitoring of the campus energy use allowed for issues to be caught and plans to be made to get the building back on track for deep savings through its pairing of energy efficiency and renewables.
Berkeley’s Zero Net Energy Library and Mental Health Clinic: From New Construction to Retrofits
The City of Berkeley’s Alice LaPierre describes the City’s experience with building California’s first zero net energy library (West Branch Library), and how the City applied best practices from that experience to their retrofit of the Mental Health Clinic.
West Branch Library
The West Branch Library was planned following the passing of a bond measure that provided $26 million in financing for four library projects, and also leveraged approximately $60,000 in zero net energy incentives from PG&E. The Library uses substantial daylighting, high-efficiency lighting and occupancy and dimming controls that are well-tuned and have received no negative feedback. Heating and cooling are provided by solar thermal and radiant floor heating with 200 gallon thermal storage, supplemented by heat pumps in months with extreme temperatures. Fixed and operable windows provide ventilation. Solar photovoltaics provide more energy than the building needs for eight months of the year – so much so that the City is in the process of installing curbside electric vehicle charging to maximize the benefit to the City of that energy. Regular commissioning and monitoring allows the City to ensure its ZNE building is operating as a ZNE building – and celebrate the findings from its first operating year’s performance.
Mental Health Clinic
Using the experience of the West Branch Library, the City reviewed its portfolio for strong ZNE candidates and identified the Berkeley Mental Health Clinic, a former mortuary. In some ways, the building posed a challenge: it has skylights in inconvenient locations, a historic tiled roof on the south facing part of the building that could not be touched, and standing water and mold issues during the rainy season. But, the City reviewed the opportunity for deep energy efficiency improvements, and the ratio of space on the roof for renewable energy to the building’s expected energy load – and found opportunity. It was estimated based on usable space on the roof (approx. 3,500 sf) that 70 kilowatts (kW) of solar could be installed (at 20W/sf), which could feasibly cover the high-efficiency needs of the building. The City commissioned a zero net energy feasibility study to confirm before designing and constructing the project. The retrofit project included high-efficiency windows and investments in insulation (including R-20 dense pack cellulose in the walls and R-30+ insulation in the attic). Through LED lighting and tubular skylights and daylighting where possible the Clinic averages 0.8 watts/sf in lighting power density. The Clinic uses a heat pump system with variable air volume VAV) fans for HVAC (supplemented by a small domestic hot water system). Finally, the building has a building energy management system (BEMS) that allows for sophisticated scheduling and controlling of building equipment. The estimated cost of the project was $525,000; final costs ended up being slightly higher but close. (In comparison, the West Branch Library’s total cost as a new construction was approximately $10 million.)
Santa Monica’s Zero Net Energy Library – and ZNE Technology Testing Grounds
Moderating the discussion, Garrett Wong from Santa Monica touched on the City’s zero net energy, LEED Platinum Pico Branch Library, and their currently-in-design zero net energy Central Administration Building, with which they are hoping to achieve the Living Building Challenge. Wong focused on how local governments can use demonstration spaces to future proof and ensure the technology investments they make in energy efficiency, zero net energy and sustainability are smart ones. Santa Monica’s Office of Sustainability has used their own 3,000sf office to demonstrate and test the use of new environmentally-friendly materials, layouts, and lighting technologies.
Takeaways Across Projects
- If we have high efficiency, zero net energy goals coming in 2020, 2030, and beyond, we need to start exploring how to fix our existing buildings and identifying efficient new construction techniques now.
- Zero net energy buildings can be cost-effective in new construction and existing building portfolios: identify what programs or policies zero net energy supports in your jurisdiction, and use modeling to identify the most cost-effective and appropriate energy-saving measures to implement.
- Matching renewable energy generation with deep energy efficiency retrofits is central to zero net energy developments. In a retrofit, be sure to understand your current building’s energy load – and strategize using deep retrofits to bring that load down before scaling your renewable generation.
- Incorporate as many passive systems as you can, from building envelope to building orientation (if new construction).
- Starting with a feasibility study was found to be useful in strengthening negotiations and feeling confident that zero net energy was feasible.
- Energy modeling is also key for considering different energy efficiency strategies and choosing the most desirable one given each building’s unique parameters.
- Sub-metering, tools for energy management, staff training, and monitoring and commissioning are critical for ensuring your ZNE-construction operates as ZNE.