Conservation and efficiency can take us far but not all the way. Even after we have reduced our energy load to a bare minimum, we will still have to meet that remaining load with some form of energy. In order to achieve climate neutrality or deep cuts in GHG emissions, campuses will need to transition as much as possible to carbon-free renewable energy technologies – solar, wind, biomass, geothermal, and hydro (though the latter is pretty much tapped out in most regions). We can either build renewable energy capacity on campus or buy green power. This section discusses on-campus renewable energy sources for non-heating and power plant applications. When performing an economic evaluation of these technologies, consider the dollar savings associated with avoiding future costs for RECs or carbon offset purchases. See the "Paying for Campus Renewable Energy Systems" section for resources describing renewable energy financing options.

5.3.1 Photovoltaic Solar Electric Arrays

Many campuses are installing photovoltaic (PV) solar electric arrays. While rarely as cost-effective as energy conservation, PV becomes more cost-effective when conventional electric rates are high and ample incentives are offered by state government or local utilities.

Obviously, the amount of available sunlight is another important factor though PV can work well in all areas. Where there is less sun, you compensate by adding panels to meet a given load. This adds cost and stretches out payback but it works. Where snow may cover panels during winter months, panels can be tilted to shed snow or PV array output can be pro-rated downward to allow for a number of weeks or months when output is nil. The performance of grid-interconnected PV is generally measured in terms of annual power production and most PV production occurs during the warmer months when days are longer and there is less cloud cover. In areas where winter days are cold and clear, angling panels to take advantage of those conditions becomes more important.

There are a variety of financial models for installing PV on campus. Your school can design, purchase and install its own system -- typically with the technical assistance of a consultant or supplier. The relatively high cost and long payback of this kind of investment can be tempered by incentive dollars that reduce the initial or “first cost” of the system. Another financing strategy is to include the cost of the solar energy system in a larger self-financing energy conservation program and, in essence, allow the energy conservation measures (and the dollar savings they produce) to pay for the solar.

Another approach for installing solar on campus is signing a power purchase agreement (PPA) with a renewable energy power provider who will install and own a PV system located on your campus. A PPA will oblige a school to purchase power from the PV system for a number of years at rates established by the contract. The primary advantage of this arrangement is that the school is not responsible for the installation, operation, maintenance, or cost of the PV system. Also, this arrangement may allow the energy supplier to take advantage of tax credits which may not be available to the campus.

Maximum output from PV arrays occurs mid-day on hot summer days – precisely the time when regional grids in many areas are under strain because of very high air conditioning loads. At these times, hourly rates for electricity may be much higher than average rates. This coincidence suggests that an analysis of PV cost-effectiveness should be sophisticated enough to factor in the additional dollar savings associated with avoiding that very expensive conventional electricity. PV arrays can also reduce peak demand and peak demand charges. PV dollar payback may still be relatively long though factoring in these additional savings will shorten it somewhat.

In order to claim a CO2 reduction from a campus owned and operated PV system or from a PV PPA, you must own the renewable energy certificates or RECs associated with the output of your system. In the case of a PV system your campus owns, you must not sell the RECs it produces but instead must “retire” them. In the case of a PV PPA, you must buy not only the power produced by the system but also the RECs (see the "Buy Green Power" section for an explanation of RECs.)

AASHE maintains a list of campus PV installations.

5.3.2 Other Solar

Other on-site, on-campus solar options include:

• Passive solar
• Daylighting
• Solar hot water

Not only can all three of these technologies be considered for new construction, all three can be either made to work or installed in existing buildings. For example, you may already have buildings with rooms or corridors with ample south-facing glass that allows solar gain during the winter months. This gain may be a nuisance now, causing localized over-heating. Building occupants may be fighting that sunlight with pulled down shades. Your maintenance staff may have solved the problem by installing reflective window film to block the sunlight from entering the building. An alternate approach would be to let the sunlight pass through the windows and put that heat to work by installing thermal mass to store it for use later in the day or by modifying the HVAC system so the heat is captured, transported, and used in another part of the building. Engineering or architecture students may want to study passive or active solar heating options for that kind of campus building as a class or volunteer project.

Similarly with daylighting, you may already have daylit spaces but are not taking advantage of their energy saving opportunity because of inadequate controls on electric lighting. Installing photocells or sensors may be all it takes to keep electric lighting off when daylight from the sun is adequate to illuminate those spaces. Facilities staff or students can survey the campus to look for opportunities of this kind.

Solar hot water systems can be more cost-effective than PV solar electric systems yet are generally less common. Why is that? Maybe it is because piping is harder to install than wiring. Maybe it’s because fewer incentives are available. Also, unlike PV (whose output can always be used by the building it’s mounted on or the local power distribution system its connected to), solar hot water systems must closely match production with demand. And hot water needs may not coincide with those times when solar hot water systems readily produce hot water. On most campuses, hot water demand predominantly occurs in the fall, winter and early spring when the fall and spring semesters are in session. However, in many parts of the country solar gain is not ideal during much of that period: the sun is low in the sky, days are short, and there may be lots of cloud cover or snow. Also, while most campus buildings have hefty appetites for electricity, not all campus buildings have adequate hot water loads to justify a solar hot water system. Buildings with above average hot water needs include athletic facilities, student residences, and food service facilities.

While solar hot water presents some challenges, it is a viable option for campuses interested in demonstrating solar energy. If the “first cost” of such a system is daunting, consider a power purchase agreement with a solar provider that would build, own, and operate “your” solar hot water system while selling you its hot water output. Students and faculty can study the possibility of using solar hot water technology for seasonal solar storage – collecting and storing solar heat collected in the sunny summer for use in the cold cloudy winter.

5.3.3 Wind Energy

Some colleges and universities have installed wind turbines on or near campus to meet a portion of their electricity needs. The huge size of the most efficient turbines, i.e. utility scale turbines whose blades reach as high as 400 feet, make them “out of scale” to the rest of a campus and hence there can be challenges to installing them on smaller campuses or near campus buildings. These giant turbines are often better suited to be installed on the periphery of a large campus or on outlying campus property. Some campuses may own distant property and that too can be considered for wind turbine installation -- though in that case getting the power to campus may involve additional delivery costs. It is generally financially advantageous to install wind energy capacity on the campus side of the electric meter.

There are a variety of wind turbine financing options to consider – from campus ownership to buying the output of an on-site turbine through a power purchase agreement – with advantages and disadvantages to each. If your campus is pursuing wind energy, it is important to design your project to take advantage of federal and state incentives, tax credits, and tariff mechanisms which are now in place and are being developed to promote wind energy as well as other renewable energy technologies. As with PV, the campus must own the RECs produced by the turbines in order to take credit for GHG emissions-free power – though it is the introduction of electricity from the turbine (not the RECs) which actually changes the mix of generation away from polluting fossil fuels (see the "Buy Green Power" section for an explanation of RECs.)

Smaller turbines which can be mounted on buildings present another on-campus wind energy option. These can make a statement and have educational value – though their output is likely to be very low given their small wind swept areas.

If your intent is to generate cost-effective electrical power from a wind turbine, then be sure to have a proper professional wind assessment done; it doesn’t protect the climate to waste a lot of steel production putting an industrial wind turbine on an unsuitable site with little wind. This is an exceptionally wasteful mistake to make because the amount of power in the wind is a function of the cube of the wind speed. Thus, even an additional meter/second in wind speed can make a huge difference! Of course, there also will be a need for training turbines, particularly at technical and community colleges, and these obviously need to be placed close to where students are. To avoid waste, these should be smaller analogs of the largest industrial turbines. Refurbished models may be cost effective for this purpose.

AASHE maintains a list of campus wind installations.

5.3.4 Biomass

See the "Alternatives to Coal" section for discussion of biomass as heating or power plant fuel. Also, students – with help from campus facilities management and relevant academic departments (e.g. chemical engineering) -- may be interested in producing biodiesel on campus using waste fryer grease from campus food service and local fast food restaurants. Students at Oregon State University provide an example of the latter.

5.3.5 Geothermal

Geothermal energy involves tapping underground reservoirs of hot water or steam for space and water heating as well as for electricity generation. Alternately, water can be pumped underground to be heated by hot rocks – though hot rock geothermal generally requires very deep wells ). Geothermal energy resources of this nature are very site specific and not available to many colleges and universities.

In contrast, geothermal or ground source heat pump (GSHP) systems are almost universally applicable. They make use of shallow wells or bore holes (up to a few hundred feet deep) to access the relatively constant temperature of the earth just below the frost line. With the help of electrically powered heat pumps and closed or open water/glycol pipe loops which exchange heat with the ground, these systems use the earth as a heat source and sink -- extracting heat from the ground in the winter and rejecting/storing it there in the summer. As such, geothermal heat pump systems are a kind of renewable energy technology. These systems can also be regarded as energy efficient technology. Unless flowing groundwater is present near the wells, applications need to have both heating & cooling loads to avoid a long term change in the ground temperature.

GSHP systems are applicable to both new buildings and existing buildings. To be cost-effective, they are best suited to buildings which require mechanical air conditioning during the warmer months. If you are striving for passive cooling, then a GSHP system may not make sense. These systems require electricity to run compressors, pumps, and fans though are much more efficient than electric resistance heating. Zero-energy new buildings become a possibility with this technology since it can be powered by electricity generated by PV panels. Achieving this measure of performance on a retrofit basis is very difficult. Depending on the CO2 emitted by your electricity source, GSHP can have a very positive impact on reducing a building’s carbon footprint vs. fossil fuel heating.

Oregon Institute of Technology provides an example of a campus geothermal installation. The National Wildlife Federation provides additional examples of geothermal heat pump-heated and cooled buildings.

5.3.6 Fuel Cells

Stationary fuel cells which generate electricity and heat are another potentially renewable option for campus installation However, fuel cells powered by natural gas – which is the norm -- are neither renewable nor carbon free. To use a fuel cell to produce GHG emission-free electricity and heat, a carbon-free source of hydrogen would be required. That could come from a hydrolysis process (which splits water into hydrogen and oxygen) that is powered by renewable, carbon-free electricity from either wind turbines or PV panels.

Fuel cells that use natural gas can function as an energy conservation measure and in that capacity reduce GHG emissions.

AASHE maintains a list of campus stationary fuel cells.

5.3.7 Renewable Energy Educational Displays

In all cases, it is desirable to accompany an on-campus renewable energy installation with an education program or display. Such a display could include metering and monitoring to show real-time performance of the system. This can be conveyed via a kiosk or website or both. Incorporating an educational component contributes to the goal of introducing sustainability and climate change into the curriculum.

It may also be possible to design an on-site solar, wind or biomass system so that it can be used for student or faculty research.

Maximizing the educational and research value of on-site renewable energy installations is a good idea in itself plus it helps compensate for the fact that in many cases these projects are very expensive and have longer paybacks and produce less carbon mitigation than would energy conservation.

University at Buffalo's “Energy for the Future” educational display is an example of a campus energy display.

5.3.8 Paying for Campus Renewable Energy Systems

The preceding discussion about on-site renewable energy options includes some discussion of financing options. For more information on financing on-site renewable energy technologies, see The Business Case for Renewable Energy: A Guide for Colleges and Universities by Andrea Putman and Michael Philips (2006), Alternative Energy Economics by Michael Philips and Lee White (2009), and the Database of State Incentives for Renewables and Efficiency.