Energy fuels innovation and Harvard's growing innovation corridor in Allston is going to need an energy system as advanced as the cutting-edge research being conducted up and down Western Avenue. To meet this challenge, the University has designed a lower-carbon, climate resistant, and highly efficient district energy facility (DEF) that's beginning to take shape behind the rising steel of the new Science and Engineering Complex (SEC).
The 58,000 square foot facility will provide a reliable source of heating, cooling, and electricity to support Harvard's academic and research activities being planned for Allston. Because they act as an in-house utility dedicated to serving campus buildings, facilities of this type also have an outsized impact on a campus's greenhouse gas emissions footprint.
How they are designed matters.
A focus on creating efficient supply and lower demand
The DEF design team focused on making the supply side reliable and highly efficient. At the same time, project teams working on the buildings focused on reducing overall demand for energy. For example, the SEC was designed by Behnisch Architekten to be one of the most energy-efficient laboratory buildings of its size, through close attention to architectural elements, the use of heat recovery systems, and other features. In fact, the new building is expected to be so efficient that during fall and spring it will use very little heating and cooling from the DEF.
Largest thermal energy storage in Massachusetts
A noteworthy element of the new DEF will be a 1.3-million-gallon tank for storing chilled water that will be used to cool buildings with some limited other applications to support research. The tank is analogous to an enormous battery because the chilled water will be produced and stored during off-peak hours, typically nights and weekends, when electricity is cheaper and less-polluting. It can then be used during the daytime when needed, lowering the burden on the power grid during peak times.
With a total capacity equivalent to 9 megawatt hours the thermal storage tank is believed to be the largest such system in Massachusetts. A previous study done by a Harvard fellow found that there is about a ten percent difference in how polluting the greenhouse gas emissions coming from the New England electric grid are from peak to off-peak times.
Prioritizing climate resiliency
The Boston region is vulnerable to sea level rise and storm surge flooding, meaning critical infrastructure such as transit and electricity services could be impacted if resiliency precautions are not taken. A climate resiliency pilot study of the Allston campus performed by Harvard’s planning department identified that future flooding would pose a significant risk for the basement location of the energy facility that was included in the original design of the SEC.
In response, Harvard re-located the DEF to an alternative above-grade location that will improve resiliency and reliability (the building is raised above projected flood levels and does not contain a basement). The infrastructure that is used to deliver the heat-energy can also better handle any potential flooding than a conventional steam distribution system, thereby further bolstering the entire system’s resiliency to climate change.
Built with a fossil fuel-free future in mind
The Allston DEF is also being built with the future in mind. It has been designed to be as flexible as possible so emerging technologies can be incorporated over time as the University works towards its climate action goals to be fossil fuel-free by 2050 and fossil fuel-neutral by 2026. The facility currently relies on natural gas because that’s the dominant lowest carbon fuel source available for this scale of facilities in the New England region. As low and zero carbon technologies are tested and proven, they can be evaluated for incorporation into the new DEF because of its flexible design. This approach will also allow Harvard and others to test innovative new ideas for reducing fossil fuel emissions from district energy systems.
"We see district energy as an enabling platform, providing us with the flexibility to make real-time adjustments based on both the carbon intensity of the grid and the fluctuating price of power," said Bob Manning, Director of Engineering & Utilities at Harvard Campus Services. "Our system will be able to optimize between on-site combined heat and power generation and purchased power, especially as the grid gets greener. With thermal storage, we can shift production to the hours when carbon intensity is low and when pricing drops or even goes negative. The round trip efficiency will be much better than current battery technology.”
A portfolio approach that allows for optimization
In describing the new facility, the project team emphasizes that flexibility was a key consideration. By employing a wide range of technologies, the heating, cooling, and electricity mix being delivered to the Allston campus can be optimized based on external conditions and energy demand.
- A heat-recovery chiller will allow waste heat from the chilled water production system to be transferred to the new low-temperature hot water heating system and used to heat buildings. Traditionally, heat from the creation of chilled water would be discarded, however through this combined cooling and heating process the heat is collected and repurposed, resulting in higher efficiencies and reduced consumption of source fuels.
- A low-temperature hot water system was chosen instead of steam because it’s much more efficient for distributing heat-energy. Additionally, with a supply temperature of 140 degrees Fahrenheit, the DEF’s hot water system provides a greater opportunity to capture waste heat from other energy technologies (e.g. solar thermal, ground-source geothermal, fuel cells, etc.), which can further reduce overall source fuel use and greenhouse gas emissions. The design parameters of the DEF’s low-temperature hot water system were chosen in collaboration with the design team for the highly efficient SEC building and will set the standard for future buildings that are constructed in the area.
- A cogeneration system will be able to produce up to 2.5 megawatts of electricity on-site and allow waste heat from the electricity production process to be transferred to the new low-temperature hot water heating system and used to heat buildings. Recovering this heat through the combined heat and power (CHP) process lowers the consumption of source fuels. The DEF also includes expansion bays for installing additional CHP equipment as demand from the Allston campus grows.
Beyond producing its own heating, cooling, and electricity, the DEF will also take electricity from the regional grid and distribute it to the Allston campus through a new microgrid similar to other ones that are already in place across campus. The solar energy projects that have been and will be installed on the rooftops of buildings across the University are also incorporated into the diverse electricity mix serving campus via these microgrids. There are already 1.5 megawatts of rooftop solar panels installed across Harvard’s campus, with many more projects being planned. To learn more about how microgrids operation read this Vox piece by David Roberts and Alvin Chang.
The new DEF is scheduled to be operational in summer 2019.