Solar, wind, ground-source heat pumps, biomass, biodiesel – there are a range of renewable and clean energy options. With pending carbon emission regulations, the reduction in climate-change impacts, available funding incentives, and long-term benefit to the bottom line, now’s the time to investigate incorporating renewable energy into your portfolio. Choosing the strategy that’s right for your building requires a clear, comprehensive approach because solutions can change from building to building (even in the same climate). The following framework will help you identify an appropriate technology that meets your financial objectives.
Your building classification influences which renewable energy strategy makes sense. For example, a Class-A office space isn’t typically a large user of domestic hot water, but has high electricity demands, making photovoltaic (PV) panels a possible option. On the other hand, a hotel uses a tremendous amount of process hot water for cleaning, which might gain more from a solar thermal hot water strategy.
Next, examine your building’s energy consumption and energy cost profiles. Is your building heating dominant or cooling dominant? What are your hot water demands? Look at your energy loads and the distribution of gas and electricity.
Renewable energy includes what’s available to harvest on or around your building, so site and surroundings definitely weigh into your decision. The climate, shape of the building, its orientation, and context (urban or rural) all play a part. Look at your available heat sources and sinks. Sunlight on the building is a heat source. A body of water next to your building is a potential heat sink. People often think of solar PV for office buildings, but a building in a dense urban environment with a small rooftop may receive too much shade from its neighbors to make PVs viable.
One way to begin the analysis is to determine how much solar energy the site can produce using PVs as a basis for comparison. PVs work well for a capacity analysis as they’re a simple, available, and mature technology. For example, if we take a building with a 10,000-square-foot footprint, but only 5,000 square feet are usable roof area, it’s an easy calculation to find the energy-generation capacity of PVs in a given locale (see Fig. 1).
Once you have your baseline calculation, you can apply it to the variety of other technologies to see how they stack up. Develop a shortlist of the renewable energy applications that provide the best return. Then, measure them against the following considerations:
Is the building capable of accepting the renewable energy technology? PVs may provide the best return in your initial assessment, but if they require structural changes to the roof, the improvement costs may outweigh performance. If you’re already using hot water for heating, and the boiler is easily accessible, biomass or biodiesel to supply the boiler may take the lead.
Evaluate the cost of the technology itself. Compare the cost per BTUs of boiler capacity for biomass vs. the cost per watt for PVs, or the per-kilowatt cost for the wind turbine.
Examine your utility rate structure. For example, if you’re located in an area that has high gas prices and low electricity costs, and you’re using gas to produce your building’s hot water, this could impact your strategy selection. Typically, it’s most effective to work with your local utility to get these questions resolved. However if the local utility is unable to help, get with an expert to work with the facilities team.
For example, here was the normalized cost of energy on a recent project (the high cost of electricity relative to cost of fuel oil led to a conversation about using an onsite biodiesel generator to produce electricity and heat recovery to produce domestic hot water):
Electricity: $4.16 per 100,000 BTU equivalent output
Natural Gas: $3 per 100,000 BTU output
Fuel Oil: $1.997 per 100,000 BTU output
Understand your area’s utility escalation. In some regions, the price of gas increases faster than the price of oil; this dynamic will have future impacts on the technology’s cost vs. return on investment.
Gauge long-term operations and maintenance costs. Look at the cost benefit based on the life-cycle of each technology. For example, a typical PV manufacturer warrants the performance of the panel for 20 years, but most panels continue to perform reasonably well beyond that point. A typical boiler is rated to last only for 15 years, but with reasonable preventative maintenance, boilers last well over 30 years (dependant on use).
Factor into your decision how much capital you have, what incentives exist, and your installation timeframe. If you aren’t planning on installing right away, a better technology could supersede your selection. Prices also fluctuate with demand. The cost of a PV panel dropped from $10 to under $6 per watt installed in the past 2 years, but creating this extremely complex technology and availability of raw materials could mean that prices tend to rise as demand goes up. However, certain technologies like solar thermal hot water systems get cheaper as demand rises. Unlike their early versions, these systems are now are extremely well resolved, yet the technology remains very easy to manufacture.
Pros and Cons
It would be short-sighted to imply that a factual analysis alone provides the right answer, as issues of goals and preferences come into play. Some building owners are captivated by certain technologies, like wind turbines, although their performance in small-scale applications hasn’t lived up to expectations, and achieving good wind energy production in an urban environment is very challenging. If PR is your objective, a visible PV array can generate widespread interest, but the fabrication of PV panels requires extremely corrosive chemicals that are detrimental to the environment. For some, the wisest move is to buy green power and invest in the infrastructure for large-scale renewable energy projects.
Adding renewable energy to your portfolio is a smart decision. Determining which one suits the building requires input from the facilities team and owner, coupled with a thoughtful evaluation of your specific situation and long-term interests.
Vaibhav Potnis, LEED AP, is the Advanced Climate Solutions team leader and a senior technical consultant at Green Building Services Inc. The Advanced Climate Solutions team develops strategies and analysis to help projects and organizations address their energy use and carbon footprints. Vaibhav can be reached at 866-743-4277 or firstname.lastname@example.org.