Energy Modeling at Harvard

See the link above for in-depth assistance with methodology, tools, case studies, and support. Energy modeling analysis allows comprehensive comparative analysis of potential building systems and strategies to create the most efficient building possible. From modeling, the team can gain a full understanding of cost and how systems interact, and can accurately analyze integrated decisions. Harvard projects that have utilized energy modeling have been able to design systems with significant energy cost savings over ASHRAE baselines. Blackstone’s energy model created a design that will produce 39% regulated savings and 90 Mount Auburn Street designed for 32% regulated savings.

HARVARD FOREST (2007) – FAS installed a 10.2 kW, 60 panel photovoltaic array at the Harvard Forest near the maintenance garage. The PV array supplies enough energy to run the garage and is connected to the rest of the buildings so that surplus energy can be utilized and a battery is not needed. The system is expected to produce approximately 12,450 kWh of electricity per year. View the system’s performance here.

MANUFACTURER	ENVIRONMENTAL BENEFIT
Evergreen Solar	Reduction of 7.8 metric tons of CO2 equivalent annually

 

SCIENCE CENTER (2007) – This is an example of a building integrated photovoltaic (BIPV) system. It is an 11.9 kW system and will provide 25% of Cabot Library's lighting needs. The system’s performance can be viewed here. Manufactured by Solar Integrated Technologies, this system can be installed at the same time as a new Sarnafil roof membrane or it can be retrofitted onto existing Sarnafil membranes, without affecting the integrity of the roofing membrane. In a retrofit, wires are put in conduit and mounted to the surface. The system has 3 SMA Sunnyboy 5000 inverters, is monitored by a Heliotronics system, and the real time data is displayed on the Heliotronics’ SunViewer.net web portal. See the Solar Integrated brochure and contact HGCI or Arthur de Cordova (Sales Executive), adecordova@solarintegrated.com, for more information.

MANUFACTURER	ENVIRONMENTAL BENEFIT
Solar Integrated Technologies, Inc.	Reduction of nearly 8 metric tons of CO2 equivalent annually

 

SCIENCE CENTER (2006) – FAS installed a Sepco single shoe box lighting system in front of the Science Center to power an exterior light. It produces 2kWh of electricity per day in summer and approximately 0.6 kWh in winter.

MANUFACTURER	ENVIRONMENTAL BENEFIT
SEPCO, Single Shoe Box Lighting System	Reduction of 0.53 metric tons of CO2 equivalent annually

 

SHAD HALL (2003) – The Harvard Green Campus Initiative, the Harvard Business School and the HBS student group, Sustainable Development Society, collaborated on the university's first PV project – the installation of a 192 panel, 36.4 kW photovoltaic array on the roof of the Business School’s Shad Hall. The Green Campus Loan Fund funded the project, along with grant money from the Massachusetts Technology Collaborative (MTC). GroSolar of White River Junction, VT installed the Sanyo 190 watt panels. The installation will deliver clean, environmentally friendly energy for 20-25 years, at a rate of about 35,000 kWh per year and at a cost of about $0.09/kWh (Y2003). The total project cost (Y2003) was $363,529 (of which the MTC Grant provided $125,997 (Y2003). Annual electricity savings are about $11,000 (Y2003), yielding a payback of 21.3 years.

 

MANUFACTURER	ENVIRONMENTAL BENEFIT
Sanyo 190 watt panels	Reduction of 22 metric tons of CO2 equivalent annually

 

Renewable energy is generated by wind, solar, geothermal, or biomass. The development of onsite renewable energy projects such as photovoltaic (PV) electric generation is of great strategic importance to the university’s sustainable planning. While the initial up front cost and payback for PV projects are both still high, PV projects can often provide the following benefits:

• PV projects secure sponsoring departments a lower cost per kWh over the array’s expected life.
• PV systems help with peak load shedding – producing the most energy during hot, sunny, summer days, which coincides with high air conditioning demand.
• PV systems provide greater electric supply reliability. Arrays are off the grid, and therefore immune to grid failures.

In addition to the system benefits listed above, PV projects demonstrate a department’s or university’s commitment to supporting innovation in building and energy design and operation.

Learn more about the following renewable energy types through our renewable energy fact sheet series:

Architectural Wind

Bioheat

Biomass

Photovoltaics

Solar Thermal

The Advanced Buildings Energy Benchmark, Section 8.9, describes optimal performance criteria for onsite renewable energy.

 

Proactive students willing to work with university administrators can conceive and achieve innovative technology. The HBS Shad Hall PV installation was a collaboration between an enthusiastic student group and multiple administrative departments. Students coordinated vendor solicitations and selection, conducted grant writing and financial planning, and made sure the project remained a priority for the HBS facility department. The HBS facilities department provided invaluable project guidance and project management expertise. The HGCI worked with the MTC to help secure grant funding and provided additional funds through the GCLF. Without a shared vision and commitment toward the university’s sustainability goals, the first PV panels installed on a Harvard building could not have been possible.

Many other technologies exist, but have not yet been implemented at Harvard, such as solar hot water heaters and building-mounted wind turbines. See a presentation by The National Renewable Energy Laboratory. Other resources include the U.S. Department of Energy - Renewable Energy.

 

PV roof tiles

Powerlight manufactures tiles that can be integrated into a tiled roof in the same way that regular roofing tiles are. More information can be found at SunPower.

SolarWall

The SolarWall® solar air heating system is a metal wall system that uses solar energy to heat and ventilate indoor spaces in new and retrofit applications. Metal cladding heats air that is collected in an air cavity. The pre-heated fresh air is then brought into the HVAC system and distributed throughout the building. The SolarWall also provides summer cooling by preventing solar radiation from hitting the building’s south wall.

Biodiesel in Boilers

Bioheat (also called biodiesel or biofuel) is a blend of heating oil and biodiesel, most often made from soy or processed used vegetable oil. It can be mixed with #2 and #6 fuel oils. B20 (20% biodiesel & 80% fuel oil) and lower percentages of biodiesel can be used in systems without retrofits. Bioheat has been successfully tested in the Northeast at many universities including Middlebury, Bates, Colby, Eastern Connecticut State, and the University of Southern Maine.

Biomass

Biomass involves the burning of biological products – usually chipped wood leftovers from sawmills, excess harvested wood, waste manufacturing wood, or wood pellets. If the wood feedstock is sustainably harvested, biomass can be considered almost carbon neutral because the feedstock sequesters carbon dioxide when it grows.

Wood pellet stoves are a good choice for urban buildings, as pellets are easier to store and more efficient (because moisture has been removed) than wood. Systems can be fully or semi-automated, eliminating the need for manual fuel handling and can be sized for residential or commercial buildings. Pellet stoves produce very little waste and the fuel is inexpensive. One drawback is supply, as pellet shortages have happened in the past.

More information can be found at Pellet Fuels Institute.

When biomass is heated in the absence of oxygen, a mixture of carbon monoxide and hydrogen, called syngas, is released. Syngas burns cleanly into water vapor and carbon dioxide.  Inorganic components, such as metals and minerals, are trapped in an inert and environmentally safe form as char, which can be used as a fertilizer.

Building-Mounted Wind Turbines

Aerovironment has developed building-mounted wind turbines for low-rise buildings. Ideal buildings have a length to height ratio of about 5:1. A 1,000W, 3 mph turbine exists now, but a 400W, 4-6 mph turbine is in production. The cost, as of March 2007, for fifteen 400 kW turbines, is about $73,000 installed. The canopies are aesthetic only and optional. Without the canopies, this system costs about $46,000. Massachusetts rebates of $2/watt ($3/watt for LEED) and $50/Mwh annually for renewable energy, allows a reasonable ROI. Aerovironment will provide feasibility studies, including wind studies for the building site, and structural analysis of the existing building. Installation time is about two days. The noise on the roof is about 50 decibels. The units move 30 degrees in either direction. They have a 5 year warranty and a 15 year life expectancy. For more information, see the Aerovironment website, their Architectural Wind brochure, or contact HGCI. For an estimate, contact Jeff Wright, Director, Strategic Global Accounts Energy Initiative.

 

Solar Thermal

Solar thermal is a blanket term for any technology that harnesses solar radiant energy for practical applications.  Solar thermal applications can provide domestic hot water, space conditioning, and even electricity.  In the US, solar thermal technology is used mainly to generate domestic hot water, although space conditioning applications have gained popularity in recent years. 

The two types of collectors that can be used in cold climates are flat-plate collectors and evacuated tube collectors. Flat plate collectors are an insulated panel through which water circulates. A dark backing absorbs solar radiation, which is transferred to the circulating water. Evacuated tube collector systems are similar, but they use a partial vacuum to assist with the heat transfer. Evacuated tubes can make better use of sky irradiation, giving them a more even output over the year; they are however inherently much more expensive. Flat-plate collectors are insulated, weatherproofed boxes that contain a dark absorber plate under one or more glass or plastic covers. Evacuated-tube solar collectors feature parallel rows of transparent glass tubes. Each tube contains a glass outer tube and metal absorber tube attached to a fin. The fin's coating absorbs solar energy but inhibits radiative heat loss. These collectors are used more frequently in the U.S for commercial applications.

Once heated in the collectors, the hot water can be used for domestic use, space heating, or even space cooling by coupling it with an absorption chiller.  SOLID Solar offers turn-key solar thermal installations and has experience with solar cooling in the Arizona desert. 

Enerworks, Inc. also provides solar hot water applications for both residential and commercial settings. See the Enerworks diagram on How it Works. Contact HGCI for more information.

 

311 ARSENAL STREET (2005) – HRES installed a 150 kW turnkey cogeneration system at 311 Arsenal Street in Watertown, MA, to save on electricity costs, and to assist with perimeter heating, pool heating, and pool room dehumidification. The system produces 1,200,000 kWh annually. The project cost was $315,000, minus a $60,974 rebate from Keyspan. The Green Campus Loan Fund covered the remainder of the cost, $254,026. Annual savings are projected to be $63,912 for a payback of 3.9 years.

MANUFACTURER	ELECTRICAL OUTPUT (kW)	THERMAL OUTPUT (Btu/h)	PAYBACK	ENVIRONMENTAL BENEFIT
TECOGEN CM-75 (2)	150 kWh	980,000	3.9 years	Reduction of 814 metric tons of CO2 equivalent annually

SHAD HALL (2003) – HBS installed a natural gas fired 75 kW TECOGEN Cogeneration Module, along with infrastructure for a second 75kW unit in the basement of Shad Hall. It produces approximately 600,000 kWh, which is about 20% of the building's annual energy use. The fuel utilization efficiency is 93.7% at LHV of 905 BTU/scf or 83.1% at HHV of 1020 BTU/scf. The up-front cost was covered by the Green Campus Loan Fund. The total project cost was $205,000 (includes infrastructure for a second 75kW machine) with a rebate of $46,500 (Y2003) from Keyspan and annual savings of $51,566 (Y2003).

MANUFACTURER	ELECTRICAL OUTPUT (kW)	THERMAL OUTPUT (Btu/h)	PAYBACK	ENVIRONMENTAL BENEFIT
TECOGEN CM-75	75 kWh	490,000	4 years	Reduction of 769 metric tons of CO2 equivalent annually

 

BLODGETT POOL (1984) – Blodgett's natural gas-powered cogeneration system is used for domestic hot water and to heat the pool. The system produces about 300,000 kWh of electricity per year. Heating costs have been reduced by about one half. A new processor was installed in 2002. The fuel utilization efficiency is 91.6% at LHV of 905 BTU/scf or 81.3% at HHV of 1020 BTU/scf.

MANUFACTURER	ELECTRICAL OUTPUT (kW)	THERMAL OUTPUT (Btu/h)
TECOGEN CM-60	60 kWh	440,000

 

Cogeneration units (small units also sometimes referred to as micro combined heat and power) use a single fuel source to generate both electricity and heat. In traditional central utility plant electrical generation, much of the fuel’s embodied energy escapes as heat during the combustion and exhaust cycles. With cogeneration units, heat produced as a by-product of electrical generation is captured and used to heat domestic hot water or air systems, dramatically increasing fuel-utilization efficiency and substantially reducing energy expenses. This efficiency, combined with the increased demand for distributed generation, has led to the production of high-efficiency cogeneration units suitable for use in a variety of facility settings. According to TECOGEN, the average central utility plant is 35% efficient, while their modules are over 90% efficient by consuming less fuel.

 

NSTAR Rebate Applications