The Putney School: Net-Zero Energy Master Plan

The Putney School Master Plan December 2011

6.0 The Net-Zero Campus With fuel oil prices tripling in recent years and with the success of the Net-Zero Field House, both the necessity and feasibility of major energy reductions have become apparent to the School. This realization led the Putney School to ask for an energy masterplan as part of the overall campus master plan. This energy plan is intended to guide the School toward a secure, affordable, environmentally responsible energy future for the campus. As part of the plan, we have developed energy standards for all future renovations and new construction and recommended renewable energy sources to meet the reduced building energy loads. The plan also outlines the necessary action steps to move toward the goal of a net-zero campus.

6.1 Strategic Energy Planning It is our opinion that the economic reality of peak oil will drastically change how we assess building and energy performance. Because energy costs have remained relatively stable, when adjusting for inflation, for a long-time, the financial reward for energy conservation and renewable energy has been modest.

However, recently, fuel escalation has been 5-15% over the life of project financing. Thus, detailed financial modeling indicates that significantly higher investments than have been common have an excellent return on investment, and a drastically reduced risk and exposure to future energy cost changes.

Not only is this likely a more secure investment, but it is obviously also good for the planet and the community. Thus, this larger initial investment might in fact be the most prudent investment and best solution.

6.2 The Path to Net-Zero The path to net-zero1 energy consists of two separate but related pieces. The first aspect of the netzero strategy is conservation, or building energy improvements. These include building enclosure improvements, as well as remediating moisture (and in some cases, mold) problems that need to be addressed for occupant health and safety as well as building durability. Additionally, moisture problems could get worse if they are not addressed as the buildings are tightened up. This requires controlling unwanted moisture entry and controlling indoor moisture generation and indoor air quality with, in most cases, new ventilation systems that do not presently exist. Mechanical systems also will need updating, not only to allow proper temperature control of spaces, but to allow the systems to be powered by renewable energy. Proper temperature control not only improves comfort and productivity, but eliminates the need to overheat parts of the building so that others are warm enough. The classic example of this is the older steam heating system, which in the winter overheat many rooms, requiring occupants to open the windows and wasting huge amounts of energy, while other rooms are hardly heated to comfortable temperatures.

The second aspect of the net-zero strategy is the addition of renewable energy sources to meet campus energy needs. Specific renewable energy systems are discussed below, but include solar electric, or photovoltaic, or PV systems to produce electricity; solar hot water systems; and biomass (wood chips or wood pellet) fired boilers for space heating and for backup for solar water heating

6.0 The Net-Zero Campus | 31

Conservation and renewables are proposed to be pursued in tandem to make progress toward the goal. In the past, the perceived wisdom has been “conservation first, renewables second.” There are three reasons this is no longer the case.

1. It is wise to take advantage of opportunities as they arise: If a building is being worked on for programmatic, deferred maintenance, or another reason, then improvements should meet the proposed energy standards so that there is incremental building improvement.

2. Outside funding should be used as opportunities become available for renewables or conservation through grants and gifts and through efficiency programs offered by Efficiency Vermont.

3. In order to address climate change, both conservation and renewables are needed simultaneously to move towards a net-zero future as quickly as possible.

We recognize that the path to net-zero for the Putney School is not an easy one. The campus’ many older buildings require repair (often urgent) and many require repurposing or remodeling, in addition to energy upgrades. Meeting all these 1

A “net-zero” campus is defined here as all building energy requirements being met by solar energy, or an annual basis. That is, photovoltaics and solar hot water systems would generate as much energy over the course of the year as all campus building energy requirements. A “carbon netural” campus would utilize biomass for a (probably large) fraction of the thermal requirements (heat and hot water), with biomass quantities that could be sustainably regenerated. If all of the wood is harvested on a renewable basis from the Putney School property, it also could be argued that this also would be net-zero as it is a sustainable yield with on-site renewable energy. The former is classified as a NZEB Class 2, and the later NZEB Class 3 in Net-Zero Energy Buildings: A Classification System Based on Renewable Energy Supply Options - available at - http://www.nrel.gov/docs/fy10osti/44586.pdf.

needs will require integrating energy improvements with all program improvements and different maintenance upgrades.

Notwithstanding, we advocate allocating resources toward a complete net-zero “fix” of fewer buildings at a time, rather than minor fixes to a larger number of buildings. There are two main reasons for this approach. First, it costs more to partially retrofit a building and then to come back and do the rest at another time. The added costs come from having to un-do some of the things done in the first round to complete the second, in addition to mobilizing the builders twice. The second reason is to accomplish tangible, visible progress by achieving the net-zero goal as each building is worked on. It is expected that it will be easier to raise funds for three net-zero buildings than for six partial building improvements. This approach also allows the School and its contractors to become more proficient at accomplishing these “deep energy retrofits,” which require a level of attention to detail that is not typical.

6.3 Putney School Energy Usage Current energy cost (for buildings only, not transportation) for the Putney Campus is projected to cost about $440,000 for 2011. In 2010 the campus used: •

800,000 kWh electricity

•

75,000 gallons of oil

•

14,000 gallons of propane

•

20 cords of wood

Carbon dioxide emissions resulting from oil, propane and electricity usage totaled 1,400 tons.

6.3.1 Building Energy Use & Energy Use Intensity In order to understand where the greatest need for improvement exists it is important to understand energy usage on the campus at a building by building level. Figures 6.3.1 and 6.3.2 look at the total energy usage by each building on the campus. All fuel types are included – oil, propane, wood and electricity -- characterized by energy in the fuels, in kWh. Figure 6.3.1 illustrates the total energy use by building, while figure 6.3.2 looks at energy use per square meter, in order to illustrate how efficient the building is for its size. Energy data utilized here is an average of the 08/09 and 09/10 academic years.

In figure 6.3.2, the range of energy intensity that is required to meet the net-zero goal is noted as two dashed red lines, at 60 and 100 kWh/sq.m-yr (19 - 32 kBtu/sq.ft.–yr). The reason for the range is discussed below.

Putney School Masterplan | December 2011

Energy Use by Building, All Energy Sources 700,000

600,000

kWh per ye ear, all sources

500,000

400,000

300,000

200,000

100 000 100,000

-

Figure 6.3.1 Energy Use by Building, All Energy Souces

Building Energy Intensity, All Energy Sources

700

kWH/sq.m-yr -- all sources

600

500

400

300

200

100

0

Figure 6.3.2 Building Energy Intensity, All Energy Sources

As can be seen from both charts, the KDU is, as expected, the highest energy user due to the inclusion of the commercial kitchen. (See appendices for recommendations for reduction.) The next three highest buildings in energy intensity, figure 6.3.2, are three small buildings, Goodlatte, Arms and Prefab Houses. This is due to cordwood consumption in these buildings, which is burned at a low efficiency and therefore drives up energy intensity. The Currier Center and the Main building are the next highest users on a total energy basis, figure 6.3.1, but the newer Currier Center has a lower energy intensity, somewhere near the middle of all the buildings.

These tables give a partial roadmap of where to begin energy reduction on the Putney School campus.

Of course there will be other reasons to choose which buildings to work on first, such as program

6.0 The Net-Zero Campus | 33

H ti E Heating Energy IIntensity t it

160

Btu/sq.ft-year

140 120 100 80 60 40 20 -

Figure 6.3.3 Heating Energy Intensity

or deferred maintenance upgrades, but from an energy perspective, reducing the largest users first will produce more immediate energy and cost savings.

A third metric of energy use is how much heating energy each building uses per square foot, or Heating Energy Intensity.

Figure 6.3.3 indicates which buildings would benefit most from building enclosure upgrades and from heating system efficiency improvements. Note the wood heated homes show up again with high heating energy use intensity. The metric used in figure 6.3.3, Btu/sq.ft.-dday refers to the number of BTU’s of energy in the heating fuel that were consumed per square foot of floor space per heating degree day. Heating degree day is a measure of how cold the climate is, approximately 7,700 at Putney. In general a value lower than 5 Btu/sq.ft.-dday indicates an efficient building, 5 – 10 a building where cost effective improvements can be made, and greater than 10 indicates significant opportunities and very large savings potential.

The following three figures, break down total energy intensity by the three building use categories on the Putney School campus, Administration and Academic buildings, figure 6.3.4; staff housing, figure 6.3.5; and student dorms, figure 6.3.6, so that energy use can be more easily compared by building occupancy type.

The following three figures indicate energy use by end use, including electricity, hot water and heat, and, in the case of the

Putney School Masterplan | December 2011

KDU, cooking for the same building use categories described before: Administration andAcademic buildings, figure 6.3.7; staff housing, figure 6.3.8; and student dorms, figure 6.3.9.

Note that in all cases, heating is the single largest energy use.

These estimated breakdowns are based on fuel usage records, equipment inventory and usage patterns. While not exact, they are sufficient to indicate how energy is being used, in an effort to better prioritize energy reduction recommendations for each building and to estimate future energy source requirements. For example, total heating loads were used to estimate how much biomass fuel would be used by the Putney School or how much PV would be needed to make the Putney School campus net-zero.

6.4 Energy Improvements When moving toward a net-zero campus, what is the optimal level of energy efficiency that should be implemented in the buildings? For a “Net-Zero” campus (Class 1 or Class 2 Net-Zero buildings) all energy must be supplied from onsite renewable sources, which as we will discuss later means photolvotaics for the Putney School campus. In this case, it makes financial sense to do all energy improvements that cost less than the cost of purchasing photovoltaics to provide the amount of energy that the improvements will save. For example, if it costs $500 to insulate a roof to R-60, and that saves enough energy to avoid installing $800 of PVs, we would put in that insulation, as the insulation is the lower cost option.

Admin + Academic Buildings, Total Energy Intensity, All Fuel Sources 700

600

500

Total kWh/sq.m-yr T

400

300

200

100

-

Figure 6.3.4 Admin + Academic Buildings, Total Energy Intensity, All Fuel Sources Staff Housing, Total Energy Intensity All Fuel Sources 700

kWh/sq.m-yr /sq.m-yr from all fuels

600

500

400

300

200

100

-

Figure 6.3.5 Staff Housing, Total Energy Intensity, All Fuel Sources Student Dorms, Total Energy Intensity All Fuel Sources 400

350

300

Total kWh/sq.m-yr Wh/sq.m-yr

250

200

150

100

50

-

Figure 6.3.6 Student Dorms, Total Energy Intensity, All Fuel Sources

6.0 The Net-Zero Campus | 35

Admin + Academic Bldgs, Energy by End Use, All Fuel F l Sources S 700,000 Cooking

600,000

Electricity 500,000

Hot water Heat

kWh/year /year

400,000

300 000 300,000

200,000

100,000

-

Figure 6.3.7 Admin + Academic Bldgs, Energy by End Use

Staff Housing, Energy by End Use, All Fuel Sources 120,000 Electricity 100,000 hot water

kWh/year

80 000 80,000

60,000

40,000

20,000

-

Figure 6.3.8 Staff Housing Enery Use by Fuel Type

Putney School Masterplan | December 2011

heat

Student Dorms, Energy by End Use, All Fuel Sources 200,000 180,000 160,000

hot water Electricity heat

140,000 kWh/year

120,000 100,000 80,000 60,000 40,000 20,000 -

Figure 6.3.9 Student Dorms, Energy by End Use

However, if adding additional insulation, to go from R-60 to R-80 will cost $300 more, and only avoids installing $200 of PVs, we would not add that extra insulation, because it would cost less to install the PVs. This, then, is our net-zero “cost-effectiveness” metric. Note that this approach is unlike typical energy conservation projects that look at “payback.” Here we look at the installed cost of the energy source versus the installed cost of the conservation measure, and choose the less costly. In general, under current market conditions this financial analysis will result in the following building efficiency standards: •

R-5 Windows

•

R-20 Below-grade walls and slabs

•

R-40 Above-grade walls

•

R-60 roofs

•

Air leakage rates of less than 0.1 cfm 50/sq.ft above ground surface area. Air leakage rates are often expressed in terms of allowable cubic feet per minute of air leakage per square foot of above-ground building surface, at a given test pressure (usually 50 Pascals or 50 Pa.) A tested leakage rate of less than 0.1 cfm50/sq.ft. is required for deep energy retrofits. A rate of 0.05 is desirable but can be difficult to achieve on existing building envelopes. We would expect the first projects accomplished to reach 0.1 and subsequent projects to approach the 0.5 level. (The Field house achieved 0.065) The air leakage goals may be adjusted for particular buildings, such as the Main Building, where it may be more costly to achieve a given level of insulation than in other simpler, less historic buildings.

Ventilation is required in all buildings that will be rehabilitated, both from an air quality point of view and to meet current building codes. Heat recovery ventilation (HRV) systems, that are now very common, allow the recapturing of up to 80% or even 90% of the heat in outgoing winter exhaust and transfer of that heat into the incoming fresh air, without mixing of air streams. High efficiency HRV’s are assumed in the renovation of every building on the Putney School campus.

6.0 The Net-Zero Campus | 37

This strategy assumes traditional fossil fuel energy costs will rise until they are at a parity with cost of energy from PV. At that point, fuel costs may not rise much further as they will have to compete with the price of energy from PVs for market share. Utilizing this logic, the cost of PVs is used for the “cost-effectiveness” test for finding the appropriate level of energy conservation. This strategy is also appropriately utilized for buildings that are too far from the central campus to be considered in a biomass based energy solution. These buildings will run on PV as soon as they are retrofit to net-zero standards.

In considering energy retrofits for each building element here we select the lower cost of conservation or renewables.

If the school adopts a “carbon-neutral” biomass strategy2 – called Class 3 Net-zero in the NREL classification scheme - heat, for the central campus buildings, would be supplied by biomass; hot water by solar hot water systems; and electricity from photovoltaics. A benefit of this system is that the level of conservation of heating energy could be lower for the buildings, since the cost of the fuel is lower. However, we believe that in the future costs of biomass may increase significantly, as increasing pressure is put on our forest resources. In addition there are many questions as to what the best balance of forest resource utilization and forest ecosystem conservation will be in the future. If forests in the northeast become stressed, as some have suggested they will, based on large scale biomass utilization, it may be advantageous to develop a plan which allows for the conservation of more forest. Additionally, we believe that the forest resource can be used responsibly, and that the best way to ensure that is to use the minimum amount of biomass, which eases the problem of harvesting sustainably. Biomass should be envisioned more as a bridge to an all-solar future than an end in itself, in which case there is a benefit to preparing buildings for solar as the only source of energy when renovated.

Due to an uncertain energy future, we strongly recommend retrofitting all buildings to the same standard, the “Net-Zero” (Class 1 or Class 2 net-zero) standard noted above. Though this decision will cost more today, it will save the Putney School a large amount of money into the future.

In general, the net-zero cost-effective level of building enclosure improvements will result in building energy usage between 60 and 100 kWh/sq.m.-yr (19 - 32 kBtu/sq.ft.–yr) for total energy utilization. Some of the older and more articulated buildings and those with historic constraints, such as the Main Building, will cost more per unit area for energy improvements, so the higher end of this range of energy use would be appropriate for those buildings. Simpler and less precious facades can be changed at a lower cost, so deeper energy retrofits are cost effective and would target the lower end of the range. As a reference point, the Field House after uses only 32 kWh/sq.m.-yr (9.6 kBtu/sq.ft.-yr). Note however that occupancy of the Field House is relatively low and temperatures are kept relatively low inside since it is primarily an exercise area, so energy use in this building is lower than if this building were occupied as a dorm or classroom.

6.5 Renewable Implementation Strategy The second part of the net-zero strategy is the implementation of renewable energy. As discussed previously, biomass sources can be utilized for thermal requirements (heat and hot water), if the goal is carbon neutrality, or “Class 3 Net-zero”, but if the goal is Class 1 or 2 net-zero, the choices are photovoltaics (PV), wind or small scale hydro. Since hydro resources are not available on the Putney School campus and the wind resources on this site make it less cost-effective than solar PV, all energy would have to be supplied from PV for this campus. PV would also be required in the carbon neutral scenario (which uses biomass for thermal needs on the central campus) for all electrical loads and to make up those thermal loads that are not feasible to be met with biomass3.

Biomass fired systems are expensive enough to install, and require enough maintenance to operate, that it is advantageous to connect as many buildings as is practical to each system to minimize the number of boiler rooms4 and fuel storage systems. A central biomass system would allow for the use of wood chip fuel, which is the lowest cost biomass fuel and the least processed, thereby requiring the least non-renewable

2

There are many different biomass scenarios, some of which may be considered carbon neutral and some may not. Because sustainable forestry actually increases forest carbon sequestration, biomass (chips or pellets or cordwood) from sustainably harvested wood can be considered carbon-neutral (or even carbon-positive.) Biomass from waste wood products that would otherwise rot can be considered carbon neutral because the carbon released by rotting is similar to that released by burning. However, biomass from wood cut in an unsustainable manner should not be considered carbon neutral, because this process would cause an increase of carbon in the atmosphere. The issue of fossil fuels used for cutting, preparing and delivering biomass fuels further complicates the matter. Additionally, fossil fuels are used for the production of renewable energy equipment, such as photovoltaic panels and wind turbines. The present analysis does not take these factors into account in the carbon emissions calculation.

3 Buildings that are too far from the center of campus or not clustered together are not canidates for a pellet-fired hydronic system, due to cost and maintenance requirements.

These buildings are typically houses, which can be served, in the biomass scenario, with pellet stoves. Since these stoves require manual filling every day, or every few days, with bags of pellets, these systems are not fully automatic. So a heat pump system is required for backup, especially for days when houses are not occupied, and once installed, may be a more appropriate primary source of heat. Also, for peripheral houses with good solar exposure, solar hot water backup would be electric; where solar exposure is poor hot water may be made with a heat pump water heater, again powered by electricity, therefore both scenarios make the case for heat pumps over biomass pellet boilers.

4

A given boiler room may contain more than one boiler, for sizing, staging and redundancy purposes.

Putney School Masterplan | December 2011

Figure 6.5.1 Campus Heating Zones for Biomass Mini-District Heating Scenario

energy to extract, process and deliver. However, plant costs are relatively high and siting can be difficult.

Because of this, we have proposed an alternative for the Putney Campus consisting of mini-district heating system “nodes� at various central campus locations, each serving several buildings. Buildings that are too far from a central location or a node, such as more remote staff housing, would require different strategies to serve thermal loads. Figure, 6.5.1 illustrates which campus buildings would be included in the central campus mini-districts and how they would be structured.

6.6 Energy Sources for Carbon Neutral and Net-Zero Options Table 6.6.1 summarizes the energy sources for each of the three renewable energy options. Alongside the table is a more detailed discussion of each energy source.

6.6.1 Solar Hot Water Solar hot water is recommended for all buildings that have appreciable hot water loads. For those with very small hot water loads, such as the administration building, an electric hot water heater (probably instantaneous if the water is not too hard) would make more sense, or if there is a biomass boiler water may be heated as a zone of the boiler. For all larger loads, solar hot water is the preferred approach. This approach is cost effective, the technology is well developed and mature, and there is an adequate delivery infrastructure. The cost of the energy provided is lower than that provided by PVs. In the coming years, heat pump hot water heaters may develop to the point that PVs with heat pump water heaters may be just as cost effective as solar hot water and may have lower maintenance. At the present however, heat pump water heaters are only available in sizes adequate for single family homes and cannot produce water hot

6.0 The Net-Zero Campus | 39

Three Renewable Energy Strategies for Putney School

Renewable Energy Type [1]

Strategy Name

Number of boiler rooms 0

Source for electrical loads PV [3]

"Net Zero" (Class 1 and Class 2 Net Zero)

Photovoltaics/ ASHP [2]

"Carbon neutral" (Class 3 Net Zero)

Biomass central

1

PV [3]

"Carbon neutral" (Class 3 Net Zero)

Biomass distributed

3 to 5

PV [3]

Central Buildings Peripheral Buildings Source for Source for hot Source for heat Source for hot heat water water Air source Solar hot water Air source heat Solar hot water heat pump w/electric pump w/PV w/electric w/PV backup w/PV backup w/PV Boilers, Solar hot water Woodstove or Solar hot water fired by w/boiler pellet stove with w/electric wood chips backup ASHP or only backup w/PV ASHP w/PV Boilers, fired by wood pellets

Solar hot water Woodstove or Solar hot water w/boiler pellet stove with w/electric backup ASHP or only backup w/PV ASHP w/PV

[1] Net zero classification system from Net-Zero Energy Buildings: A Classification System Based on Renewable Energy Supply Options , Shanti Pless and Paul Torcellini -- http://www.nrel.gov/docs/fy10osti/44586.pdf [2] ASHP = Air Source Heat Pump.

[3] PV is most likely all ground mounted, inlarge arrays, possibly at several locations, net metered to all buildings on campus Table 6.6.1 Three Renewable Energy Strategies for the Putney School

enough for a dormitory or kitchen. Solar hot water is currently more cost effective, but only marginally so, for single family homes so the comparison should be watched as the plan is implemented over time.

Pro’s of Solar Hot Water: •

Only “current” solar energy is used, whereas biomass uses solar energy stored over the last 10 – 100 years.

•

Requires no non-renewable input for fuel transport.

•

Lower cost per unit of energy delivered than PV systems

Con’s of Solar Hot Water:

5

•

Requires electric backup, and therefore some PV associated with the system

•

Must be located on or near the building where hot water is needed

•

Requires periodic maintenance, (mostly checking of pH in antifreeze)

•

Location must have solar exposure which some houses do not have currently thus some trees would need to be cut, or a heat pump water heater could be used with PVs at another location

6.6.2 Photovoltaics (PV) Photovoltaics are the “gold standard” of renewable electricity.

The environmental and visual impact of these systems are as low as it gets for renewable electricity generation systems.

The technology and delivery infrastructure is mature and the systems should require very little maintenance5. PVs can be installed incrementally, as funding is available. PVs do take significant outdoor space, but they can be located at multiple locations, to reduce the visual impact of any given array and to locate the fields as well as meeting the capacity requirements for the closest electrical connection.

While wind energy is available at a lower cost for large turbines – 1 to 3 megawatt (MW) capacity – there is not enough wind at the Putney School for these very large systems, and siting them elsewhere is contentious. The Vermont Group Net Metering laws do allow large scale installations anywhere on the utility grid that serves the school to be metered directly to the school, therefore developments of community based wind, wind installations funded by the users of the energy, as opposed to by a third party or electric utility, should be monitored over the years to come, but at present this should not provide the basis for a future energy plan. In the future, community wind may become a strong alternative, and the magnitude of the electrical load at the Putney School may still be large enough at that time to make sense in relation to such a project.

Proper grounding is standard for lightning protection, but additional lightning protection should be evaluated for cost and track record.

Putney School Masterplan | December 2011

Pro’s of Photovoltaics: •

Only “current” solar energy is used, whereas biomass uses solar energy stored over the last 10 – 100 years.

•

Requires no non-renewable input for fuel transport.

•

Very little maintenance is required , and none on a regular basis (as is required with biomass systems)

•

May be located anywhere on campus that is reasonably close to power lines, preferably threephase lines.

Con’s of Photovoltaics: •

Relatively high cost

•

Large area of land required for PV installation: about 6 acres would be required for a one MW (megawatt, or 1000 kW) system. About 0.75 MW (4.5 acres) of installed would be required for electric loads for the biomass options and about 1.25 MW (7.5 acres) for the all PV option.

6.6.3 Biomass – Wood Chips Vermont has been a national leader in heating schools with wood chips. The fuel cost is very low and the energy sources and jobs created are local. The technology and delivery infrastructure are mature and the systems are reliable. The storage of wood chips requires a lot of volume, as deliveries are by large tractor trailer trucks, and it is advisable to be able to store two full loads at a time. This “bunker” system for chip storage requires space, as indicated in figure 6.6.2, as well as the space required for tractor trailers to turn around. The boiler room requires a tall stack, which can have a significant visual impact. A large distribution system would have to be installed to connect all the central buildings to the biomass plant.

Biomass plants do operate reliably, but they also require regular operator attention. A cash flow analysis, included in the appendix document 7.3.1 Putney School Energy Usage 22 Nov 11, will include these costs. . Computer based control systems can be set up to monitor the system remotely to reduce the effort required by the operator.

Fuel could be produced from the Putney School forests, even if not by students, but by a contracted forester, who would assure sustainable forestry practices. When chips are purchased on the open market, they may be cheaper but it is more difficult to insure that sustainable Area for Central Biomass Wood Chip Plant harvesting practices are used consistently. Progress is being made in area, sq.ft.

Boiler room 960 (24x40) this direction, however, with standards Chip bin 1764 (42x42) beginning to be developed. Since wood Truck access drive 4200 (42X100) chip fuel is local, we anticipate that (100' x building width) costs will escalate more slowly than other fuels, but the certainty of this is assumes 15' wide road going by end of truck quite low. Because of the uncertainty access drive for turnaround, otherwise need ~50' at we use similar fuel escalation rates as end of road other fuels in analysis of future costs.

Table 6.6.2 Area for Central Biomass Wood Chip Plant Pro’s of Central Biomass - Wood Chips: • Biomass uses solar energy stored over the last 10 – 100 years.

•

Lowest energy cost renewable source considered feasible to the Putney School in the near terms, lower cost per unit of energy delivered than PV, considering fuel costs over time as compared to cost of installing PVs

6.0 The Net-Zero Campus | 41

•

Lower initial cost than an all PV system

•

Fuel could be obtained from the Putney School property or from other local sources

•

Chips are the least processed biomass fuel that can be burned automatically

•

Very clean burning

•

Future costs expected to rise more slowly than other thermal fuels

Con’s of Central Biomass - Wood Chips: •

Requires ongoing fuel supplies and therefore ongoing fuel cost, as compared to PV where energy would be free after the initial investment is made

•

Requires a very large location on the central campus for heating plant with chip storage and tractor trailer truck access

•

Requires tall smokestack, depending on location

•

Requires regular maintenance and checks by the system operator

•

funding for renovations. This rapid deployment would allow the school to cut costs of fuel quickly, from the oil which is currently used. . Once the building is renovated, the excess heat could be exported by a relatively inexpensive underground piping system to a nearby building not powered by renewable sources. Or the boilers could be removed and employed elsewhere if the building is shifted to photovoltaic-powered heat pump system.

There is some movement now toward the production of dried, smaller wood chips, as compared to large green chips currently used in central plants. If this occurs, this fuel source could likely be utilized for a lower cost in some of the available pellet boilers. This would lower the energy input of the fuel production and could possibly be produced on site. Such chips are being produced in Europe now, and there is interest in producing them locally.

Pro’s of Distributed Biomass - Wood Pellets: • Biomass uses solar energy stored over the last 10 – 100 years.

•

Lower cost per unit of energy delivered than PVs, considering fuel costs over time compared to cost of installing PVs

•

Lower initial cost than an all PV system and a lower installed cost than a central wood chip heating plant

•

Pellet boilers can often be easily located in existing mechanical rooms and pellet storage bins can be provided by outdoor silos or in basements

•

Simple fuel delivery

•

Current pellet boilers requires little maintenance

•

Very clean burning

•

In the future, equipment that is installed MAY be able to be run on locally produced, dried, smaller wood chips

•

Can be installed incrementally, in comparison to a central wood chip plant that requires a significant initial investment

Requires substantial initial investment in plant and distribution system

6.6.4 Biomass – Wood Pellets The last few years have seen a revolution in the US in the wood pellet boiler field, with numerous excellent boilers being imported from Austria in particular, as well as other northern European locations. These boilers operate virtually automatically: they clean their own ashes into a bin; turn themselves off and on; have sensors in the flue gases to modulate air and fuel inputs for optimal efficiency and lower emissions; and they interface with modern computer based control systems. This technology is mature, though relatively new to the northeast U.S. As a result, the installation and maintenance infrastructure is continuing to develop, but mature enough to rely on this hardware. The wood pellet manufacture and delivery infrastructure is established and growing, so costs will be competitive. A large wood pellet producer is located near the school in Jaffrey, NH. The major downside of wood pellets is that the costs are significantly higher than wood chips per unit of energy produced – about double. We assume that pellet costs, which now are about 2/3 of the cost of oil per unit of energy, to rise at a similar rate as oil. On the other hand, the systems can be put in quickly in small modules, or with modular boilers linked together. Pellet storage systems are small, using silos outdoors, or, increasingly, prefab or custom bins in basements. These systems can be deployed easily and quickly to meet present heating needs, before a larger building on campus has the Putney School Masterplan | December 2011

Con’s of Distributed Biomass - Wood Pellets: •

Requires annual fuel supplies and therefore annual fuel cost, as compared to PV where energy would be free after the initial investment is made

•

Higher fuel cost than wood chips

•

More processed fuel than wood chips, requires more non-renewable inputs (7 – 15% of fuel value of pellets, depending on source)

•

Requires regular checks by the system operator

•

Requires some investment in a plant and distribution system, but much less than a central system (shorter distances and smaller pipes)

6.7 Predicted Future Energy Usage Based on the assumptions that 1) changes will be made to the Putney School buildings in accordance with the standards described in section 6.4 Energy Improvements and 2) one of the options for a whole campus energy strategy will be pursued, the Putney School will see a dramatic reduction in its campus energy use. Table 6.7.1 indicates this change and details how much of each fuel source would be utilized under each of the energy scenarios. Table 6.7.2 compares the energy usage, energy intensity, energy cost and CO2 emissions for the campus as it exists today and for the three campus energy strategies for the future. It can be seen here that the energy use, energy intensity, energy cost and CO2 emissions are the lowest under the net-zero, all-PV strategy. Further detailing the points as described above, figures, 6.7.3, 6.7.4, 6.7.5 and 6.7.6 indicate campus energy use, energy intensity, energy cost and CO2 emissions respectively.

Putney School Energy Use Futures - By Fuel Type Energy Source

Description

As Is [1] All PV's PV s [4]

As Is Major conservation + all PV with ASHP's Wood Pellet + PV Pellet Nodes + major + Solar DHW [2] conservation+ PV

Oil gallons 66,000

Wood Chip + PV + Central Wood chip plant Solar DHW [3] + major conservation + PV

Propane gallons 16,000

Firewood cords

Electricity Wood Pellets kWh [5] 780,000 60

15

Wood Chips tons 0

0

0

15

1,150,000

0

0

0 0

0 0

15 15

702,000 702,000

246 5

0 541

[1] Assumes 20% load reduction in heating and 10% reduction in electricity [2] Assumes factor of 3 heating load reduction, 10% reduction in electricity and 50% solar hot water, and PV's for all electricity use Peripheral buildings [[3]] Assumes same load reductions as #2, with all backup p from pellets. p p g still using g some fossil fuel, and PV's for all electricityy use [4] Assumes factor of 4 heat load reduction, heat pumps with COP=2.3 for heat and COP=2.0 for hot water backup, and PV's for all electricity use [5] District heating piping w/assumed 15% piping loss; mini-district system to have 10% loss. 60 tons pellets for 2011 pellet conversion at Main Bldg

Table 6.7.1 Putney School Energy Use Features by Fuel Type

Putney School Energy Use, Energy Intensity, Energy Cost and CO2 Emissions Option

As Is [1] All PV's [4]

Description

Campus Energy Use

Energy Intensity

Annual Energy cost, 2011 rates

MMBtu/yr [6]

[8]

14,000

kWh/sq.m-yr [7] 236

4,000

67

($49,000)

7,000

118

$60,000

130

7,000

118

$28,000

70

As Is Major conservation + all PV with ASHP's

Wood Pellet + PV + Solar DHW [2] Pellet Nodes + major conservation+ PV Wood Chip + PV + Central Wood chip plant Solar DHW [3] + major conservation + PV

$319,000

CO2 Emission Tons per year[9] 1,300 0

[1] Assumes 20% load reduction in heating and 10% reduction in electricity [2] Assumes factor of 3 heating load reduction, 10% reduction in electricity and 50% solar hot water, and PV's for all electricity use [3] Assumes same load reductions as #2, with all backup from pellets. Peripheral buildings still using some fossil fuel, and PV's for all electricity use [4] Assumes factor of 4 heat load reduction, heat pumps with COP=2.3 for heat and COP=2.0 for hot water backup, and PV's for all electricity use [6] All Fuels [7] ASHP's result in lower energy intensity due to COP of heat pump requiring less than half the energy to operate [8] F For allll b buildings, thermal a negative happens ildi th l fuels f l only. l PV's PV' show h ti costt due d to t paymentt for f PV electricity l t i it exportt assuming i similar i il ffraction ti exported t d (75%) as h now at the Field House [9] Energy Cost, Energy Content and CO2 Emissions of Fuels Oil gallons Btu/unit CO2 content/unit Cost/Unit Cost/MMBtu

Propane gallons 136,000 22 $3.85 $28.31

91,500 13 $3.00 $32.79

Firewood Electricity cords kWh 22,000,000 0 $200.00 $9.09

3,413 1.2 $0.13 $38.09

Pellets Chips PV-Electricity tons tons * 16,000,000 8,200,000 3,413 105 21 0 $230.00 $44.00 $0.23 $14.38 $5.37 $66.97

Table 6.7.2 Putney School Energy Use Futures and Energy Intensity

6.0 The Net-Zero Campus | 43

Campus Energy Use MMBtu/yr, All Fuel F lS Sources 16,000 14,000 MMBtu/year u/year

12,000

Figure 6.7.3 Campus Energy Use MMBtu/yr Note that wood chip systems have slightly higher piping losses than pellets due to longer piping runs. PV use is lowest due to COP of 2.3 for the heat pumps; that is, they produce 2.3 times the heat output as electrictiy input.

10,000 8,000 6,000 4,000 2,000 As Is

All PV's

Wood Pellet + PV + Solar DHW

Wood Chip + PV + Solar DHW

Energy Intensity kWh/sq.m-yr 250

kWh/sq.m-year .m-year

200

Figure 6.7.4 Energy Intensity kWh/sq.m-yr Note that because of the COP of air source heat pumps, as described above, the all PV scenario has the lowest energy intensity of all options.

150

100

50

As Is

All PV's

Wood Pellet + PV + Solar DHW

Wood Chip + PV + Solar DHW

Annual Energy Cost at 2011 Rates $350,000 $300,000 $250,000 $$/year

$200,000

Figure 6.7.5 Annual Energy Cost at 2011 Rates Note that while non-zero, costs for biomass are not very high with micro-load buildings. Negative cost reflects payment from utility for exported electricity.

$150,000 $100,000 $50,000 $0 -$50,000

As Is

All PV's

-$100,000

Putney School Masterplan | December 2011

Wood Pellet + PV + Solar Wood Chip + PV + Solar DHW DHW

CO2 Emission Tons per year

1,400

MMBtu/year Btu/year

1,200 1,000 800 600 400 200 As Is

All PV's

Wood Pellet + PV + Solar DHW

Wood Chip + PV + Solar DHW

Figure 6.7.6 CO2 Emission Tons per year Note zero emissions from operation of PVs. Note also that wood pellet emissions are higher than that of wood chips due to the increased energy used to produce the more hightly manufactured pellets.

6.8 Financial Analysis What does this all cost and what is it worth? This is an easy question to ask, but tough to answer! This analysis must take into account the cost for the building energy efficiency upgrades, the installation of biomass systems, the installation of PVs, the costs for solar hot water and the costs for the installation of air source heat pumps. When everything is accounted for the total cost for each energy scenario is as follows: •

Net-Zero, All-PV - $18,700,000

•

Carbon-Neutral, Wood Pellets - $15,500,000

•

Carbon-Neutral, Wood Chips - $16,400,000

The full detailed costs of each of these three scenarios can be found in table 6.8.1. Based on the DEW Cost Estimate, appendix document 7.2.1 Complete Final Putney 1.3 Estimate Report 11-18-11, and the work of Andy Shapiro this table indicates the full up-front cost for all three of the energy scenarios for the Putney School.

Predicted Energy Scenario - Total Costs

Name

Net Zero / PV

Description

Cost for Efficiency Upgrades [1]

Cost for BioMass Systems [1]

Costs for PV's [2]

8,757,000

$

$ 6,571,429

$

$

8,757,000

$ 1,991,000

$ 4,011,429

$

8,757,000

$ 2,872,000

$ 4,011,429

More load reduction $ + all PV/HP's

Carbon neutral Pellet Nodes + wood pellets major load reduction+ PV Carbon neutral Central Wood chip plant + major load wood chips reduction

-

Costs for Solar Hot Water

Costs for Air Source Heat Pumps [1]

Total Cost

295,000

$ 3,032,000

$ 18,700,000

$

295,000

$

472,000

$ 15,500,000

$

295,000

$

472,000

$ 16,400,000

[1] from DEW - Putney Master Plan - Building Upgrades excel document.

Pellet system and piping costs based on recent cost experience with the pellet system for the Main Building Costs for Air Source Heat Pumps include electrical service upgrades where appropriate.

[2] Based on 1.05 kWh/year per peak Watt installed; cost of $6 total per peak watt installed (before tax credits, if available)

Table 6.8.1 Predicted Energy Scenarios - Total Costs

6.0 The Net-Zero Campus | 45

Two present value summaries are presented in table 6.8.3 and 6.8.4. Full cash flows, on which these are based, can be found in the appendix document 7.3.1 Putney School Energy Usage 22 Nov 11. The first of these summaries, table 6.8.2, illustrates the present value of energy costs for the next 30 years. The campus as-is scenario includes oil, propane, electricity and cordwood being consumed consistently at the same rate as the campus utilizes today. The future scenarios include PVprovided electricity, cordwood (for at least cooking in the wood oven) and/or wood chips and wood pellets. The future scenarios also assume significant reductions in energy, as detailed in section 6.7 Predicted Future Energy Usage.

Negative values in the above table represent costs to the Putney School., while positive values indicate income. The net-zero,

all-PV scenario actually shows an income of $2,660,000 to the school over this 30 year period which is made possible by the utility requirements to pay approximately $0.06 per kWh exported to the grid. In comparison, note the extraordinary cost, $14,910, 000 over 30 years, of doing nothing to improve the School’s energy future.

Two versions of net-present values are illustrated in table 6.8.3, one at 5% real escalation and one at 10% real escalation.

Since one cannot know the future, we present both, with our assumption being that the future will fall somewhere in between these two rates. Inflation is assumed to be 2%, and a discount rate of 3% was used. The development of this table includes several assumptions, as described below.

Putney School 30-yr Present Value of Energy Costs -- All Fuels [5] Low Escalation (5%) High Escalation (10%) Campus As Is ($13,000,000) ($14,910,000) Net Zero PV [6] $2,660,000 $2,660,000 Net Zero Wood Pellets ($3,360,000) ($7,940,000) Net Zero Wood Chips

($1,720,000)

($3,860,000)

[5] Includes electricity, oil, propane, cordwood, pellets, wood chips and cost of added or savings from decreased maintenance. All fuels escalate at the same rate (5% or 10%), up to cost of energy from PV, except cordwood, which goes with general inflation only. Includes $0.06 credit per kWh exported [6] Savings due to decreased maintenance and payment for exported electricity 6.8.2 Putney School 30-yr Present Value of Energy Costs - All Fuels

Putney School 30-yr NPV of Investment [5] Campus As Is Net Zero PV Net Zero PV w/ tax credits [8] Net Zero Wood Pellets Net Zero Wood Pellets w/ tax credits [8] Net Zero Wood Chips Net Zero Wood Chipsw/ tax credits [8]

Low Escalation (5%) ($13,000,000) ($2,690,000) ($142,523) ($5,020,000) ($3,420,000) ($4,450,000) ($2,850,000)

High Escalation (10%) ($14,910,000) ($780,000) $1,780,000 ($7,690,000) ($6,090,000) ($4,680,000) ($3,080,000)

[5] Includes cost of full implementation plus cost of electricity, oil, propane, cordwood, pellets, wood chip fuels and cost for added or savings from decreased maintenance. All fuels escalate at the same rate (5% or 10%), up to cost of energy from PV, except cordwood which goes up with general inflation only. Includes $0.06 credit per kWh exported [8] 40% combined Federal and State credits. No accelerated depreciation credit is taken.

Applied only to PV cost 6.8.3 Putney School 30-yr Net Present Value of Investment

Putney School Masterplan | December 2011

1) The entire cost of all improvements – major energy conservation and new renewable energy systems is incurred in the first year. More likely implementation would be phased, but since the timing is uncertain, we show costs in year one.

2) The Putney School is paying for all the improvements. When fundraising is completed to pay for improvements, it could be argued that there is limited cost to the Putney School.

3) There is no value to the Putney School other than monetary savings on energy. The less easily quantified values include: •

Improved indoor air quality which improves health

•

Reduced or zero carbon emissions

•

Nation-wide visibility as a “green” school

•

Improved ability to attract students

•

Elimination of future fuel cost anxiety

It is difficult to place a dollar value on these attributes. There are studies attempting to evaluate the monetary values of these attributes, but these values are not included here. Despite these rather clear additional benefits, the question will always be asked “Are the costs worth the savings?” meaning a cashonly analysis. So a cash-only net present value is presented in table 6.8.3. The full cash flows (18 pages) supporting this summary can be found in the appendix document 7.3.1 Putney School Energy Usage 22 Nov 11.. Net present values assume full installation costs (less tax credits where so noted) and includes added or reduced costs for maintenance by system type, fuel cost (oil, propane, cordwood, pellets or chips), and income from PV payments by electric utilities.

As can be seen, if the 40% combined State and Federal tax credits can be taken, by donors, for the cost of the PV system, the NPV is positive for either low or high escalation rates for the net-zero, all-PV scenario. Capturing this credit would involve a third party owning the PV systems and leasing them to the school, in essence functioning as a utility for the school. This arrangement is often set-up by nonprofits to be able to take advantage of the tax credits. For-profit businesses can also take an accelerated depreciation benefit, which is not reflected here, in order to leave some financial benefit for the donor who would participate in such an arrangement. (This benefit also varies by tax bracket.)

Oil Cost, Putney School As Is $1,400,000

$1,200,000

$1,000,000

$$/year

$800,000

$600,000

, $400,000

$200,000

$0 1

2

3

4

5

6

7

8

9

10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

Year

6.8.4 Oil Cost, Putney School As Is

6.0 The Net-Zero Campus | 47

A host of assumptions go into this analysis, as noted above.

Another of these assumptions bears mention. It should be noted that energy costs for fossil fuels cannot be expected to escalate indefinitely. Basic economics would indicate that when the price for energy from oil goes above the price of energy from photovoltaics, one of several things is very likely to happen: other synthetic fuels will be priced to compete with PV, energy users would switch to PV for energy, or fossil fuel prices would be capped at this level. The cash flows all assume that this cross-over happens, and when it does, oil (or its substitute) will escalate at the general inflation rate. This happens sooner with the higher fuel cost escalation rate, as can be seen in figure 6.8.4. (All cash flows presented are in nominal dollars.)

These scenarios can, of course, be run with varying assumptions. The authors have chosen what seem to us the most plausible, in consultation with the Putney School.

Summary of Costs, Cash Flow and Present Value Analysis As can be seen, there is extraordinary financial benefit to the Putney School in securing a stable, renewable energy future.

The all-PV scenario has the lowest present value of future energy costs of all the scenarios explored in this document – indeed there are no energy costs and the school receives payments for production of the renewable electricity. This same scenario also has the highest net present value (NPV,) which includes cost of installation in the analysis, even recognizing the significant benefits to the School that are not captured in such an analysis. If tax credits can be captured, this scenario has a positive net present value at the lower fuel escalation rate, and it is the only option with this outcome.

It is an extraordinary outcome that the all-PV approach can have a positive net present value. This outcome points the way to a renewable, secure energy future for the Putney School.

6.9 Recommended Net-Zero Strategy There are a number of factors that impact the recommendations here for the energy future of the Putney School. These have been touched upon previously and are synthesized below.

•

•

PV energy source has the lowest long term environmental impact, lowest operating cost and lowest maintenance, but it also has the highest installation cost.

The central biomass system costs more than biomass nodes, but fuel cost is lower over time. Siting may be problematic and there is a large investment in piping

Putney School Masterplan | December 2011

•

Biomass nodes offer an incremental option for installation, allowing system to be built up over time, while staunching the flow of dollars going into oil.

•

All scenarios benefit from “micro-load” retrofits or “deep energy retrofits”

•

Funds are likely to be raised incrementally.

•

Future biomass costs are unknown, but likely to increase in proportion to fossil fuel increases.

•

Future regional energy demand and availability – electric, fossil and biomass – are unknown, as are future costs for PVs.

In recognition of the above factors, we recommend the following direction for the Putney School’s energy future: 1. Perform micro-load retrofits whenever a building (or portion of building) is worked on in any capacity.

2. Install biomass nodes in largest users, as is currently being done for the Main Building. As building energy usage is decreased with energy upgrades, pipe woodpellet heat to adjacent buildings to make use of boiler capacity, as is being done with the Main building and the future piping extension planned to the KDU. Having one or two such systems installed will give practical experience for the school’s operators, and these systems can pay for themselves in as little as 5 years in fuel cost savings. It may be as long or longer than five years until all buildings can get micro-load retrofits so the investment in the pellet boilers is not lost, even if the campus moves to an all-PV energy source in the future.

3. As soon as is practical, retrofit one or two peripheral buildings with micro-load building enclosure retrofits, air source heat pumps (ASHP) and solar hot water, to gain experience with this approach. Preferably one larger and one smaller peripheral building would be chosen for this process.

4. Concurrently, raise funds for PV arrays, and install in chunks as funds become available and as outside funding opportunities present themselves 5. Continue to raise funds for and implement microload retrofits, ASHPs, solar hot water and PVs, concentrating first on peripheral buildings and any central core buildings not served (or not serve-able) by biomass systems. The final step would include the addition of ASHPs and SHW to the central buildings first served by biomass systems, after they receive

micro-load retrofits.

6. Develop an annual monitoring protocol. This monitoring protocol will become incredibly important as changes begin to be made on campus to track the effectiveness of each of the measures that are pursued.

7. Annually review the net-zero plan with the net-zero team to check-in on progress in the previous year and prioritize projects for the upcoming year. As the world changes some of the assumptions presented in this report will change and will require a reprioritization of the process.

8. Update the full net-zero plan every five years to address the changing world of energy prices and technologies and to continue to make the most advantageous decisions for the Putney School.

The strategy laid out here lowers fuel costs in the short term, moves toward a net-zero or carbon neutral future, and preserves flexibility to accommodate future unknown conditions, which will affect the choices available and the factors favoring these choices. For example, if in the future, electrical supply on the grid is severely constrained, the best environmental, and possibly financial, choice for Putney School could be to export more electricity and use more sustainably harvested biomass for heating.

IN SUMMARY: Begin where you can, at the scale you can. Gain experience with new techniques and new technologies incrementally, before embarking on large projects. Be persistent in moving toward the best possible future, retaining flexibility as you go.

6.0 The Net-Zero Campus | 49