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Created and produced by DanBihn.comWork funded by the U.S. Forest Service, Colorado Governors Office, and the Colorado State Forest Service

Flex Energy for Buildings is a simple design support process that helps you and your team design buildings with the flexibility to adapt to the changing shape of energy in the 21st century — because your design decisions today can make adapting to this change easy and affordable, or needlessly difficult and expensive.

When the time is right, your Flex Energy Building will affordably...

9 Shift from fossil fuel heating to electric ground-source heat-pumps (GSHP) or District Energy.

9 Accommodate on-site renewables such as photovoltaics (PV), Solar Heat, and Biomass.

9 Accommodate thermal energy storage (TES) systems so you can buy electricity when it is cheapest and use it when you need it.

9 Integrate electric vehicles (EV) into the building’s park-ing lots and energy systems.

Designing buildings that adapt to the changing shape of energy in the 21st century

Flex Energy for Buildings

Flexibility is no accident. You might not be ready to invest in these technologies today – and some of these technologies might not be ready for you. But just because the timing isn’t right doesn’t mean you can safely ignore them.

If you aren’t designing in the ability to accommodate these low carbon energy technologies, you may be inadvertently designing them out. And buildings that cannot easily and affordably adapt are likely to become a burden to the owners and their communities.

Good news! A little planning goes a long way.Simply knowing today how you’ll add key energy technologies tomorrow, will help insure you aren’t inadvertently designing them out.

Change is coming to our energy infrastructure. Will your building be ready?

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Flex Energy Worksheet Rev. 0.9 6/1/2009 3

FLEX Energy Worksheet Default Calculation Results

In your area, a flat PV systems has a capacity factor of . To meet the annual electricity needs of your project, you will need a system with nameplate (as rated by UL®) capacity of kW (peak). For typical panels with an efficiency of 15%, you will need about sq. ft. of panels. Inverters of this size system will need roughly

sq. ft. inside your electrical room.

A vertical loop field (bore field) for a building of sq. ft. in climate zone will need roughly sq. ft. with an Energy Recovery Ventilator (ERV), and roughly sq. ft. without an ERV.

Centralized chip-fired biomass boiler systems between 1,000,000 and 5,000,000 BTU/hr take at least sq. ft. Fuel for these systems is typically delivered in an 56’ semi-trailer truck. If your building has a smaller demand, a pellet system is generally recommend. 36’ delivery trucks are common. You will need an MER. roughly sq. ft. near a potential deliver site.

An ice Thermal Energy Storage (TES) capable of storing enough thermal energy to cool your building for a design sum-mer day of ton-hours will need roughly sq. ft.

A parking lot with electric car stalls which are designed to deliver 10 miles of electricity over a 4 hour period will have a peak electrical demand of kW.

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A sq. ft. swimming pool in your location typically needs a solar thermal system of approximately sq. ft. to provide 50% of the annual heating demand.

Doubling the mechanical equipment room area will require adding an additional

sq. ft.

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Wood chip-fueled centralized boiler plants work today in many places around the country. There is good chance you can visit a working systems within a day’s jour-ney.

Most wood-fueld systems today use direct combustion to create a flame in a fire-box. The heat is transferred to water or steam by a boiler and then to the building’s heat distribution system.

Here’s what a typical working chip system looks like for a building or campus of 50,000 to 1,000,000 sq. ft.:

Wood and wood systems are not compact. Wood chips are delivered by truck – 35 to 69 feet long – into to a below-grade storage bin (some above-grade systems have been made). These storage bins are typically designed to handle 7 days of fuel during the coldest part of winter, which can mean 50 tons or more (3 MMBTU/hr) of wood requiring 4,500 cu. ft. – about 21’x 21’x 10’ – of storage.

From the storage bin, the chips are then transported to the of the boiler’s firebox by a series of auger or conveyer belts (sometimes both).The boiler itself is not too different in size compared with a natural gas system. Ramp-up and down times are longer, and this may impact your control strategy.

Hot water (sometimes steam) is delivered to the building or buildings. Chilled water can be created using an absorption chiller.

Sometimes these systems are physically integrated into the building, but more often are separated buildings.

Wood Chips

to building

Wood boilers are proven technology that works in many locations around the US. This 3 MMBTU/hr system heats 100,000 sq. ft. of office and shop space in Long-mont, CO. The biomass boiler is in the foreground, the natural gas back-up boilers are in the background.

Wood boiler and fuel handling systems are larger and more complex than gaseous or liquid fuels – making them more costly to build and maintain.

However, in many parts of the country, the lower cost of wood fuel makes wood boiler systems a solid investment.

The entire wood boiler systems are often put in a sepa-rate building connected by hot-water or steam loops (district heating), for both new and existing buildings.

Design Challenge: Adding a Biomass Boiler System

Decision Framework Flex Energy HandbookFlex Energy Worksheet

Your Design Process

Property Area: Sq. Ft.

From PV Watts 2.0

Solar Radiation

kWh/m2/day


FLEX Energy Worksheet Description & Anticipated Energy Demand

Briefly describe your building project (use, location, etc.):

General

Building Area:

Annual Electrical Usage:

Annual DHW Usage:

Electrical

Heating

Cooling

Hot Water

Number of Parking Stalls:

Roof Area:

Sq. Ft.

Sq. Ft. Peak Electrical Demand:

1000 x kWh

kW

Peak Cooling Demand:

Tons-hrs/dayAverage Summer Day:

Tons

Peak Winter Day Usage:

Average Winter Heat Usage:

Peak Heating Demand: BTU/hr

BTUs

BTUs

Swimming Pool Size:

Gallons

Sq. Ft.

Total MER Area: Sq. Ft.

Climate Zone: 4 5 6 7

Bethke Elementary School is a prototype elementary school for the Poudre School District. It will service grades K-5in a core learning format. The school is located in a new residential development outside the town of Timnath, CO.

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The building design includes a PV system large enough to provide 100% of the annual electrical demand.


Design Challenge: Adding Photovoltaics (PV)

The location of sq. ft. of unshaded area suitable for PV. At least sq. ft. must be roof-mounted (covering at least 65% of the roof area). The remaining sq. ft. can be on covered parking or stand-alone structures.

Will the roof support 5 pounds per square foot on the designated roof areas?

Show:

How will the panels be connected to your electrical system? Where will the inverters be located? Have you added any conduit to your build-plan?

Tell:

What aesthetic considerations have you made for adding PV? Do you think your building with PV added with be acceptable to your community?

The above is designated on these construction documents:

19,965 13,000

6,965

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②③

④

Flex Energy Handbook (Rev 3.1 04/01/2015)

It’s easy to be flexible. Here’s how...

Flex Energy Worksheet & Your Site PlanEnter your building’s basic energy-related data. You can start with rough estimates and goals, then update your entries with actual values from your energy model when you’re ready.

The Flex Energy Worksheet automatically calculates “reserved areas” and a few other guidelines for you and your team to use during your design process.

As part of your design process, you and your team place the “reserved areas” on your site plan and roof plan, adjusting your design as desired.

When you’ve decided how your building will adapt, enter your strategy into the worksheet and save it. That’s it.

❶

❸

❷

❹


Scale. Some technologies such as photovoltaics (PV) can work economically at both small and large scale, allowing systems to be located where there is both supply and de-mand – often on the unused roofs of buildings.

Timing. Wind and Solar energy create electricity when the wind blows and the sun shines, not necessarily when the energy is needed. As the percentage of these resources increases, the real-time cost of electricity will become more volatile: when the wind isn’t blowing and the sun isn’t shin-ing, the cost of electricity may be significantly higher than on a sunny, windy day. Thermal energy storage (TES) sys-tems are a practical way to use electricity when it is cheap and avoid using it when it is expensive.

Proximity. Modern fossil fuel power plants that economi-cally utilize a significant portion of the otherwise-wasted heat (known as co-generation, co-gen, combined heat and power, or CHP) can have a 50% smaller carbon footprint than electric-only power plants. This thermal energy can be transported several miles through District Energy distribu-tion pipes to heat and cool your building.

Your Building and The Changing Shape of Energy in the 21st Century

Systems that use natural gas, or other fossil fuels, for heat-ing will shift to electrically power heating systems like ground-source heat pumps (GSHP), or on-site Biomass or Solar Heating.

Over the life of your new building, conventional carbon-based energy sources are likely to become more expensive due to decreasing sup-

ply, increasing global demand, and carbon regulation. Simultaneously, new low-carbon energy sources are likely to continue to become less costly due to technological improvements, growing economies of scale, and public investment and policies. The result is likely to be a significant

The carbon footprint of transportation can be reduced by shifting to electric vehicles (EV) charged at the owners’ home and places like schools and offices. Additionally, EVs connected to a charging station in your building’s parking lot can be an important part of the buildings energy storage. When the real-time price of electricity is high enough, you might be able to buy back some of that energy from those cars cheaper than you can buy it from your utility.

Electric Generation Space Heating

Transportation

and persistent shift towards a new low-carbon energy infrastructure.

This change in energy infrastructure will impact buildings in 3 key areas: electric generation, space heating, and transportation. Buildings with the flexibility to affordably accommodate these changes will benefit their owners, operators, and communities.


PV

How will you add these technologies to your building after it is built?

Photovoltaic (PV) panels continue to get cheaper, but they require a relatively large area with an unobstructed view of the sun. Rooftops, when designed properly, can be one of the lowest cost ways to mount PV – especially if PV is integrated directly into roofing material. But there is a sig-nificant difference in value between a PV friendly roof and an arbitrarily designed roof that faces the wrong direction, at the wrong angle, or has roof-mounted HVAC equipment that needlessly shade otherwise useful area. The good news

GSHP Ground-source heat-pumps (GSHPs) are one of today’s most efficient electric heating technologies – and can easily provide air-conditioning, too. As the electric grid moves to lower carbon sources of electricity, the carbon footprint of this method of heating decreases. But, the ground loop fields – which thermally connect the system to the stable temperature of the subsurface soil – can require significant amount of area. Reserving an area near your mechanical

Thermal Energy Storage (TES) systems allow your building to manage energy costs by storing thermal energy when the electricity is cheapest and avoiding using electricity when it is most expensive – a scenario very likely as the electric grid increasingly relies on energy from the sun and wind.

TES

Electric vehicle (EV) charging stations can provide both a desired service for the people who use your building, and potentially give your building the ability to buy back energy from those vehicles when the real-time price of electricity

EV

is that it is not hard to design a high-value PV-ready roof.

In the future, if you want to supply your building’s average annual electricity needs using PV (net-zero), you might need more space than even a well-designed roof can pro-vide. In that case, a PV covered parking area can be a good choice. But, the parking area will need to have good solar access, too.

room that can one day be bored or excavated (e.g., garden, parking lot), can reduce the cost of adding GSHPs later.

Integrating a GSHP system with your existing HVAC system can be easy if your thermal and electrical distribu-tions systems are designed with this in mind and if there is room in for the small heat pumps that would be distributed throughout your building.

But, TES systems tends to be large and cannot always be easily integrated with all HVAC designs. Designing it in today, can help you save retrofit costs tomorrow.

is high. If you can install the needed electrical wiring and hardware without needing to repave your parking lot, you can save retrofit costs.

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District Energy (DE) systems deliver thermal energy to local energy customers using steam, hot water, or chilled water in buried insulated pipes. Downtown Denver has one of the first systems in the country dating back more than 125 years. The town of Pagosa Springs has a small geother-mal system that circulates hot water from their natural hot springs; the city of St. Paul, Minnesota, has a combined-heat

District Energy

Or these technologies?

Breakthroughs and innovation will likely present new op-portunities for you to manage your energy costs. Adding general flexibility to your building is important. How will you expand your mechanical room if needed? How will you

Breakthrough?

Biomass Biomass from wood or agricultural waste – especially if the supply is local and reliable – can be a credible fuel for on-site low-carbon heating and even cooling. Direct combus-tion technology continues to evolve into cleaner and more efficient systems, and emerging gasification technology promises even further emission reductions.

Solar Heating Solar Heating (also known as solar thermal) converts solar radiation directly into heat which can be used for heating water, heating swimming pools, heating buildings, and in some cases even cooling buildings. It is a very practical technology for buildings with swimming pools and large hot water demands (e.g., showers, laundries, kitchens), as well as space heating for garages and warehouses.

But, biomass systems are generally several times larger than natural gas or heating oil systems, and fuel delivery and storage takes significant space, which if not planned for, can be very expensive or impractical to add later.

and power (CHP) system that uses wood chips, and the Colorado School of Mines is heated with excess heat from the CHP system at the nearby Coors brewery. If there is potential in your area for this type of system to be built or expanded in the future, it can make sense to plan on sys-tems that can be connected later.

Solar heating systems require significant area with good solar access. Roof mounted hot water systems can place significant additional weight loads on buildings.

add larger electrical and thermal distribution lines through out your building if needed? This flexibility can often be added today at little extra cost.

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Invest in the Immediate

Invest in promising systems and technologies that are difficult to add to your building after it’s built. For example:

◊ Build Solar Ready Roofs & Install Conduit◊ Right-size the Mechanical Rooms and make sure you know how to

expand them when necessary.◊ Choose a different (and potentially more expensive) HVAC system

that is much easier to adapt to the future.

Prepare for the Probable

Design-in Future Flexibility – often at no additional cost beyond the time it takes your team to think through the process. Modify your ini-tial design – locations, positions, etc. to make it easier to add solutions later.

Postpone the Painless

The good news is that you don’t have to do everything today. If it is easy to add after your building is built, consider waiting – saving your money for the hard stuff (above), especially if that technology is getting cheaper.

A Decision Framework

Sometimes adding the flexibility you want will require an investment – larger conduit, a larger mechanical room, stronger roofs. Often these

investments are modest, but not always. How will you decide which invest-ments to make? The above chart gives you a place to start.

◊ If it is difficult to upgrade later and it is a very promising technology, consider investing today to enable it tomorrow.

◊ If it is easy to upgrade later IF you made a few design changes today, make them.

◊ If its easy to add tomorrow without significant modification, don’t worry.

Finally, document your design decision and the locations of “reserved areas” on your construction documents to keep your building ready for the future.

Document your Decisions

Now that you know how your building will adapt, document your de-cisions in the Construction Documents. Clear documentation will help protect your building’s flexibility from inadvertent changes.


PV (photovoltaic) is solid-state technology that directly converts sunlight into electricity – with no moving parts. PV panels work at nearly any scale – just a few to power a communication shack, a dozen or two to power a home,

GSHP (ground-source heat-pump) technology is a very efficient way to heat and cool a building using electricity. Because GSHPs move heat rather than generate heat, it is more than 3 times more efficient than conventional electric

Biomass is solid fuel made from plant matter such as wood, agricultural waste, and energy crops. The biomass is usu-ally burned on-site to create heat (and sometimes cooling). While this releases CO2 into the atmosphere, it is the same

TES (thermal energy storage) typically make ice for storing cooling capacity, or hot water for storing heat. This allows a building to create thermal energy from electricity when it

EV (electric vehicles) are at least 4 times more efficient than conventional cars. Even when the electricity used to charge an EV is generated at a distant coal-fired power plant, an EV can still have a smaller carbon footprint than a gasoline

PVG

SHP

TES

Biom

ass

EV

CO2 that the plant absorbed from the air when it was growing, so biomass is referred to as “carbon-neutral.” When all the other energy “inputs” are taken into account, in most cases, biomass is still a low-carbon energy source.

or thousands to power a community. But, no matter what scale, PV only produces electricity when the sun shines. The cost of PV is fall-ing and they may become one of the cheapest sources of electricity within a decade.

boilers or baseboard electric heaters. It is actually more efficient to run a GSHP system with electricity generated by a distant natural gas power plant, than it is to directly use the natural gas to heat a building.

is cheapest (usually at night), and use that thermal energy whenever the building needs it.

powered car. EVs may become a key part of the solution to the en-ergy storage challenge presented by resource-driven renewables such as PV and wind. EVs will be an important component of a smart grid.

A brief overview to give diverse design teams a common understanding of key Flex Energy Technologies

Flex Energy TechnologiesDi

stric

t District Energy (DE) systems deliver thermal energy through pipes in the form of steam, hot water, or chilled water. Many industrial processes and electric power plants create significant amounts of heat, which is often wasted,

Ener

gy that can be used to heat and cool nearby buildings. By using this “waste” energy, total system efficiency can be doubled and the environmental impacts of fuel use cut in half.

Power PlantInverter

PV Panel

DC AC

Average Power

TotalEnergy

PeakPower

Noon 6 PM6 AM


Visualize Adding Photovoltaic (PV)

PV (photovoltaic) technology directly converts sunlight into electricity. PVs are solid-state so there are no parts to physically wear out – and, while the material does age, most technologies (and there are many) are expected to last between 20 and 50 years. Many PV panels are guaranteed for least 20 or 25 years. The technology is still expen-sive at around 20¢ per kilowatt-hour, which is 3 or 4 times more than wind power or electricity generated from natural gas. The good news is that PV is getting cheaper each year. It will almost certainly be an important energy option for your building in the coming decade.

PV has the lowest operational environmental impact of any existing technology – and the environmental impact of manufacturing PV is considered very manageable. Ac-cording the to the National Renewable Energy Lab, the energy payback is currently between 1 and 3 years. Energy payback is number of years it takes a panel to generate as much energy as was used to make it.

If the sun was shining directly overhead all the time, a 100 watt PV panel would generate 100 watts all the time (though system losses may reduce this by 10 % to 20%). While this is the case for PV panels in Space, in Colorado the average amount of sunshine is equivalent to a little bit less than 5 hours of full sunshine a day. So the average amount of energy gen-erated by a PV panel is about 20% of its maximum (or nameplate) value – a 100 watt panel averages about 20 watts throughout the day and the year. So, if your home needs 25 kWh per day, you’ll need a 5kW system – costing around $25,000.

PV panels generate DC electricity (48 volts for a panel is common). In order to connect a PV sys-tem into your building’s electrical systems, it must be converted by an “inverter” to AC that exactly matches the electricity from the utility.


Visualize Adding Photovoltaic (PV)

FLEX CHECK 9 Is your roof designed to have the best solar resource?

9 Will your roof support an additional 5 lbs. per sq. ft.?

9 After you add all the PV, will your community be satisfied with the aesthetics?

9 Are most of the roof-top HVAC equipment on the north side of the building to reduce shadows on the PVs?

9 How will the DC wires connect the PV panels to the inverter[s]?

9 Do you have room in your electrical room for the inverters?

9 Are your parking spaces located on the south side of your building so you can add PV parking covers?

9 Consider a roof type friendly to PV. For example, PV can be mounted on a standing seam metal roof at a very minimal cost, while some other roof types can be quite costly.

9 Having the inverter located within 100’ of the PV panels helps minimize energy losses and cabling costs.

9 PV panels mounted at a tilt equal to the site latitude (40 to 60° in Colorado) can generate 20% more energy than flat-mounted panels. Consider designing roofs at or near this angle.

9 Inverters can be as tall as 7’ and heavy. Consider access heights and structural loading.

Workbook User Notes for PV.The workbook calculator gives you estimates for the electrical and physical size of a PV system needed to provide a target percentage of your building’s annual electricity needs (default is 100% for a Net Zero Electricity building).

The default PV Generation Efficiency - the annual amount of electricity 1-kW of PV panels generate - is determined using the popular and well-regarded online tool, PV Watts 1.0, which is provided by the National Renewable Energy Laboratory (NREL), in Golden, Colorado. The default value of 1,300 is for a flat-mounted system with a 0.8 DC-to-AC derating for a system in Boulder, CO.

If you’d like to experiment with other location and roof angles, please visit http://rredc.nrel.gov/solar/calculators/PVWATTS/version1/US/Colorado/ . Select the nearest city to your site. Enter a DC Rating of 1.0 kW in the PV System Specification section, and 0.8 in the DC-to-AC Derate box, press Calculate, then use the AC Energy (kWh) in the Year row at the bottom of the results section.

http://rredc.nrel.gov/solar/calculators/PVWATTS/version1/US/Colorado/

http://rredc.nrel.gov/solar/calculators/PVWATTS/version1/US/Colorado/

Heat Pump

Heat Pump

Hot or Cold Air

Hot or Cold Air

Hot or Cold Air

Heat Pump

50-60˚F

Vertical Ground Loop Field Circulation Pump

300 feet

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Heat Pumps are distributed through out the building, provide heating and cooling.

Ground Loop Field consists of pipes in direct thermal contact with the subsurface ground. The loops can be either vertical (300’ deep is common), or horizontal.

Circulation Pump moves water (usually mixed with anti freeze) through out the system connecting the heat pumps to the mild-temperature subsurface ground - which is what makes the system very e�cient.


Visualize Adding a Ground-Source Heat Pump (GSHP) System

Ground-source Heat Pump, GSHP, technology is a very efficient way to heat (and cool) your buildings with electricity. Because GSHP moves heat

instead of generating heat, it is more that 3 times more efficient than conven-tional electric resistance heat (e.g., electric boilers, electric baseboard heaters).

GSHPs fit into the low-carbon energy infrastructure of the 21st century by replacing on-site fossil fuels such as natural gas, propane, and heating oil, with electricity – electricity that is increasingly be generated from carbon-free sourc-es such as wind and solar. Even today, a GSHP system that gets its electricity from an efficient natural gas power plant, can have a carbon footprint about half that of an on-site natural gas boiler or furnace.

And GSHP can make solid economic sense today – especially in buildings that also require cooling.



FLEX CHECK 9 The ground-loop fields is big – a 60,000 sq. ft. building might need 30,000 to 40,000 sq. ft. for a vertical bore field. Do

you know where you would place this field?

9 In some locations, EPA regulations and other site-specific conditions may prohibit vertical bore holes.

9 How close in the bore field to your mechanical room?

9 A typical heat pump is about 25,000 BTU/hr, uses 2.4 kW, and has dimensions of about 24” x 28” x 88” . Do you know where you will put these units?

9 How will you add the distribution piping to your building? These pipes connect the circulation pump in your mechani-cal room to each of the distributed heat pumps.

9 What is the soil conductivity of your site? If you’re planning to install GSHP in the near future, getting this tested will be important in determining the feasibility and actual size of your system.

9 Consider providing medians in the parking area, lining them up so that GSHP boreholes can be easily added after park-ing lot is paved.

9 Because GSHP (and solar thermal) provide lower temperature heat than conventional boilers, they require larger heat transfer surfaces (baseboard radiators, fancoils, etc.). Consider initially installing these larger components to make upgrading less expensive.

9 Consider radiant in-floor heating. It is a very good match for GSHP, solar thermal, as well as conventional boilers.

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Electric boilers and electric baseboard heaters directly convert electrical energy to heat. They are essentially 100% efficient – for every unit of electrical energy used, one unit of heat energy is generated.

Heat pumps move heat, they do not generate it. Electrical energy is needed to do this (and generates some heat in the process), but heat pumps typically move more than three times as much energy as they use.

Heat Pumps vs. Electric BoilersHow a Heat Pump Works

An air-conditioner is a heat pump that operates in only one direction: cooling the room by moving heat from the inside of the building to the outside. Gener-

ally, though, heat pumps work in both direction – so they can move heat from the outside into the building for heating as well. And by moving heat, instead of gener-ating it, heat pumps can be as much as 3 or 4 times more efficient than conventional electric boilers or electric baseboard heaters.

These systems work by moving heat between two coils – one located inside the building, the other located outside the building. The smaller the temperature differ-ence between these coils, the less work the heat pumps need to do – and therefore, the less energy it uses.

In climates with mild winters, it is possible to heat a building efficiently by putting one coil outside, directly exposed to the air (usually with a fan blowing air over it). These are called “air-coupled” or “air-sourced” heat pumps.

However, in places like Colorado, where a cold winter day or night might be 0°F, the difference between the inside air and the outside air is too large for an air-sourced heat pump to work efficiently.

Fortunately, the ground temperatures in Colorado 10 feet below the surface and deeper, generally stays between 50°F to 60°F throughout the year. By pumping heat from the subsurface ground – instead of the outside air – the temperature difference is small enough for the heat pump to work efficiently. The outside coil is thermally connected to the subsurface ground by circulating water with anti-freeze through piping buried underground and then across the outside coil. This ground loop water is about the same temperature as the ground – and so the difference between the outside coil and the inside coil is around 20° to 30°F, which a heat pump can very efficiently deal with.

GSHPModern CoalPower Plant 93% Efficient

210 lbs of CO2

1-MMBTU 0.363-MMBTU 1.09-MMBTU

0.61-MMBTU

0.726-MMBTU

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210lbs/1.09 MMBTU =

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Delivered Electricity Delivered Heat

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Combined CyclePower Plant GSHP

110 lbs of CO2


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110lbs/1.674 MMBTU =

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Waste Heat

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Transmission Loss Environmental Energy from Ground


C.O.P. 3.0

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110 lbs of CO2

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Why this is becoming important...Heating with a GSHP powered by electricity generated by a mod-ern natural-gas fired power plant has carbon footprint nearly 50% smaller than directly heating with an efficient gas boiler or furnace. Why? GSHP work by moving heat, not generating heat.

However, heating with a GSHP powered by electricity generated at modern coal plant, will have a larger carbon footprint than burning natural gas in a boiler or furnace. Still, GSHPs are at least 3 times more efficient than using a conventional electric boiler or electric baseboard heaters (electric resistance heat).

The Good NewsColorado’s electricity grid is getting greener. By 2020, at least 20% of Xcel Energy’s electricity will come from non-carbon renewable energy. So, as the carbon footprint of the grid gets smaller, so to does your heating footprint. And if you choose to install PV on your building or purchase 100% renewable energy from your util-ity, your footprint will be even smaller.

Colorado has a “Net Metering” policy that allows an excess PV energy generated in the summer to be carried over for use in win-ter. Combining PV, GSHP and this policy is an economical way to provide solar space heat.

Where does the this “free” energy come from? Unless you’re near a hot spring or other true geothermal phenom-ena, the reason the subsurface ground is around 50° to 60°F is because of the sun. It is this “environmental energy” that makes GSHPs efficient. (The Coefficient of Performance, C.O.P., is the ra-tio of heat energy delivered for every unit of electrical energy used. A C.O.P. of 3 is common, and this number is improving.)

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Make Ice at Night When Electric Rates are Low

Compressor

Ice Tank

IndoorsOutdoors

Use (melt) Ice During the Day When Electric Rates are High

Compressor Fan

Midnight 6 AM Noon 6 PM Midnight


Visualize Adding a Thermal Energy Storage (TES) System

Thermal Energy Storage, TES, is a practical technology for reducing electricity costs by making and storing thermal energy (heat or cold) when electricity is

cheapest (usually at night), and then using the thermal energy whenever your building needs it.

To cool buildings, ice-based TES systems are often used. These systems make ice at night when electricity is cheap and then melt the ice to cool the building in the middle of the day when electricity is most expensive.

The good news is that making ice isn’t difficult. Many, but not all, conventional chillers can do this without costly modification – basically, just add the ice storage tank.

The bad news is that these tanks are large and may not integrate into your HVAC sys-tem unless you’ve planned for it.

Conventional (compressor-based) air-conditioning uses electricity when your building needs cooling –

often when electricity costs the most.

By adding a Thermal Energy Storage (TES) ice system, you can provided cooled air to your building when it’s needed, and buy the electricity when it’s cheapest.



FLEX CHECK: 9 Can your air conditioning compressor make ice? Not all compressor can. Having the wrong type of compressor will

increase your retrofit costs significantly.

9 Where will you locate a TES system? These systems are large and often located outside to building. The closer to your mechanical room, the more efficient and cheaper the system will be.

9 TES systems are heavy. Don’t expect to put them on your existing roof.

9 If your utility doesn’t currently offer time of use pricing, it will likely make more sense to hold off on a TES system until they do.

9 Ice storage tanks can be located inside or outside the building. If you’re considering locating them inside the building, be aware that they can be 8’ or 9’ tall and 10’+ wide. Consider how you would get them in your building.



Why this is becoming important...As the electric grid becomes increasingly powered by renewable energy such as wind and solar, the cost of electricity will increasingly fluctuate during the day. All other things being equal, when the wind blows, costs will be less than with the wind is still.

When the sun isn’t shining or the wind isn’t blowing, the electric utility may need to do one or more of the following:

• Use power plants that consume increasingly expensive fossil fuels such as natural gas. And build new power plants that better match the variable needs of the a lower carbon grid.

• Build large electric storage systems, such as pumped storage system that pump water from a lower dam into a higher dam to “charge” the system when there is a surplus of electricity, and run the water back through a conven-tional hydro-electric generator to “discharge” the system when the electricity in needed. These systems are only about 50% efficient.

• Send price (or control) information in real-time to encourage customers to consume at lower cost times (e.g., at night when the wind might be blowing) and avoid high cost times (e.g., on a hot, windless summer afternoon when a cloud passes over). This an important role of a Smart Grid.

If your building can respond to the utilities’ price signal and buy electricity when it is cheapest, your building will not only save money in the short term, and re-duce the need for the utility to make expensive investments.

This TES system is installed at Colorado State University.

Key Point: These systems take significant space and are heavy (they’re filled with water). Designing a building that accommodates TES is not difficult, but it is no accident.

Wood Chips

to building

BoilerRoom

Wood Chips

Wood Pellets


Visualize Adding a Biomass Boiler System

Biomass boilers systems directly burn solid biomass – wood chips, wood pellets, agricultural waste, and energy crops – to heat (and even cool) buildings. These

systems are working in many places around Colorado. They can be very clean and cost-effective.

The fuel itself is carbon neutral – the carbon released during combustion is the same carbon that the plant or tree absorbed from the atmosphere when it was growing. Even when the carbon from harvesting, transportation, and sometimes growing are proper-ly accounted for, this is almost always a low-carbon source of energy. And often there are additional community benefits.

For larger buildings and campuses (100,000 sq. ft. or more), wood chips are a great solution.

For smaller buildings, wood pellets make sense.



FLEX CHECK 9 How will you integrate the boiler system with your current HVAC system?

9 Wood chip systems are often housed in a separate boiler building. The distribution pipes can be expensive ($100/foot or more). How far is your boiler from your current mechanical room?

9 Chips and pellets are delivered by truck. Turning radius for a semi-trailer truck with a 42’ trailer is 27’ for a 90 degree turn. Can a deliver truck access your storage area during normal business hours without disruption?

9 On-site chip and pellet storage can take significant space – ideally located next to the boiler room. For pellets, a 6 ‘to 9’ diameter grain silo is common.

9 A 200,000 BTU/hr pellet system needs about 4.5’ by 8.5’ (38. sq. ft. per unit) inside your mechanical room. Can a pellet boiler be added without significant construction?



Wood Chips.Wood chips are an attractive fuel because of their low cost – the direct result of the low processing effort needed to make them - just run a tree through a grinder or chipper, and if the wood is dry enough, you have instant fuel.

The downside is that handling solid fuel – especially irregular chips with occasional twigs – is not easy and the systems are not cheap. The bottom line is that the economics seldom make sense for build-ings smaller than 100,000 sq. ft. A small system is about 3 MMBTU/hr and can cost upwards of $1M. The physical footprint of the boiler system with room for a week of fuel can take up at least 1,200 sq. ft.

Getting that fuel to the boiler needs planning. Wood chips are de-livered by truck – 35 to 69 feet long. Access during business hours is required if you want to keep your costs low.

Wood Pellets.Wood pellets are an attractive fuel because they are very easy to handle – the direct result of the high processing effort needed to make them. Wood is chipped and dried to a precise moisture con-tent, then turned into a fine sawdust flour, which is then extruded by a machine initially developed to make pet food (that’s why wood pellets look rabbit food). And that’s why this fuel cost several times more than chips.

Their regular, small size makes it very easy to build automatic deliv-ery systems. Since wood pellets are nearly the same size and weight as corn kernels, agricultural equipment is often used – helping to reduce the system costs.

Systems ranging from 100,000 BTU/hr to 1,000,000 BTU/hr can be very practical – if pellet can be affordably delivered in bulk, not in bags.


Visualize Adding Support for Electric Vehicles

Electric Vehicles (EVs) and Plug-in Hybrids Electric Vehicles (PHEVs) are very likely to become an important part of personal transportation. And they may also

become a very important part of your building’s energy management strategy.

Electricity, as a transportation fuel, is 3 or 4 times cheaper than gasoline (electricity at $0.10/kWh is equivalent to gasoline around $0.90 /gallon).

Even when the electricity is generated from coal power plants, the carbon footprint is less than gasoline (due mostly to the high efficiency of the electric motor system). And if the electricity comes from renewable sources such as PV or wind, the operating carbon footprint is essentially zero.

EVs are generally charged from standard house current (120 V or 220 V), although rapid charge systems that use higher voltages are being tested. Charging a mid-sized EV in 8 hours will easily demand more than 3 kW. 100 such EVs will demand about 1/3 of a megawatt – which could even be more than the demand of your whole build-ing.

The emerging “smart grid” facilitate intelligently and dynamically coordinating sup-ply and demand (potentially through real-time price signals). It will allow the EVs in your parking lot to not only buy electricity from your building, but there may be times when your building buys power back from those EVs.

And, unlike petroleum based fuels, almost all the energy resources (fuel, etc.) that power the US’s electric grid come from domestic sources.



FLEX CHECK 9 A “conventional” EV can demand at least 3 kW electric service for a slow (overnight) charge. A 100 vehicle parking lot

may need 300 kW service. How will you upgrade your electrical sevice?

9 Is there room for an additional service transformer next to your current one?

9 How will you install a smart changing stations in each parking slot? (These charging stations will probably be a bit big-ger than a conventional parking meter. )

9 What will your parking lot look like? If you install the conduit when you excavate the connecting area form the electric room to the parking lot you can save the expense of doing it later.



210 lbs of CO2

1-MMBTU 0.363-MMBTU 450 miles

0.61-MMBTU

0.39-MMBTU

210 lbs/450miles =

0.467 lbs CO2/mile 0.027-MMBTU

Waste Heat

Coal

Transmission Loss

Delivered Electricity Delivered Distance

Modern CoalPower Plant

EV

1,240 miles/MMBTU (4X )

93% Efficient

35 MPG Car310 miles/MMBTU

Gas

171 lbs of CO2

1-MMBTU (8.85 gallons)310-miles

171lbs/310 miles =

0.554 lbs CO2/mile

Delivered Distance

Gasoline

19.4 lbs./gallon113,000 BTU/gallon

93% Efficient

Combined CyclePower Plant

110 lbs of CO2

1-MMBTU 0.558-MMBTU 692 miles

0.4-MMBTU

0.6-MMBTU

110lbs/692 miles =

0.159 lbs CO2/Mile 0.042-MMBTU

Waste Heat

Natural Gas

Transmission Loss

Delivered Electricity Delivered Distance

EV

1,240 miles/MMBTU (4X )

These diagrams show that an EV can be both more energy ef-ficient and have a smaller carbon footprint that a conventional gasoline powered car.

On average, less than 20% of the energy in a gallon of gasoline is delivered to a car’s drivetrain. An electric vehicle can easily deliver 80% of the electric energy used to charge the batteries.

The average American drives about 33 miles a day. A reason-able size EV might get 4 miles per kWh. That works out to about 8 kWh/day - about a third of what a typical home uses.

That means that a two car household will use about 60% more electricity than it does now. This will be a huge problem for the electric grid if that peak occurs at the wrong time. But if the EVs are charged intelligently when other demands are low, today’s electric transmission and delivery grid will be able to handle this new demand.

Combined Cooling,Heat & Power Plant

Chilled Water

Hot Water or Steam

Thermal EnergyElectric Energy


Visualize Connecting to a District Energy (DE) System

District Energy (DE) includes district heating and district heating. It is an old technology with a promising future. Typically, centralized energy plants distrib-

ute thermal energy through underground pipes in the form of steam or hot water for heating, and chilled water for cooling. DE systems range in size from small campuses with 100,000 sq. ft. of building area, to the Xcel Energy system in downtown Denver (providing heat since 1880 – one of the oldest working systems in the country – and providing cooling since 1998).

In some cases, it is more cost-effective to create heat and cooling in central location rather than in each building (and back when Denver installed its heating system that meant coal could be delivered by train to a central location rather than being delivered to each basement by horse-drawn cart).

Why the interest in this old technology? As we try to reduce the carbon intensity of our energy infrastructure, one of the biggest opportunities is to utilize some of the wasted thermal energy generated as a by-product of conventional electric power plants (when coal is burned to generate electricity, only 35% of that energy is converted to electricity, the rest is heat that is usually just released into the environment).

Besides the district energy plant in downtown Denver, the Colorado School of Mines in Golden is heated by excess steam from the near-by Coors brewery which generates electricity and process steam at an efficiency greater than 55% (almost twice as effi-cient as a typical power plant).

Many building in downtown Pagosa Springs are heated with hot water from the hot springs the town is famous for.

And, most of Colorado’s large college campuses are heated with district energy systems – usually using natural gas.


Visualize Connecting to a District Energy (DE) System

FLEX CHECK 9 Piping thermal energy can be expensive. The shorter the distances, the cheaper the system. How far away is your me-

chanical room from the likely district energy service entrances?

9 District Energy systems typically distribute energy using water (hot and or chilled). Can your HVAC system can easily integrate DE without retrofitting the distribution system?

9 Just because your new building is far from other buildings today, this can change over the life of your building. You still need to consider this option.