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KNOWLEDGE GUIDES

For Architects

XCO2 Energy 2009 www.xco2energy.com

CHP Engine

Grid

Input Process Output Eciency

60

80

96

30

50

30

Heat

Electricity

Boiler

Conventional

Energy Network

Combined

Heat and Power

(CHP)83%

ElectricityGeneration

HeatGeneration

57%

Losses 10 units

Losses 50 units

Losses 16 units

Coal Power Station

50

units ofelectricity

units ofelectricity

units ofprimary fuel

units ofprimary fuel

units ofprimary fuel

units ofheat

units ofheat

02: Combined Heat and Power/Trigeneration

Combined heat and power (CHP) is a system where heat, which is usually lost during the electricity

generation process, is recovered and used. This results in much greater overall eciencies than grid-supplied electricity and, thereore, carbon emissions are usually reduced. In addition, a trigeneration system

can convert the waste heat into chilled water or cooling uses with the inclusion o an absorption chiller.

Building Scale CHPCHP is generally suitable or the

ollowing types o building due to

their high constant heat demand:

Hotels

Hospitals

Leisure Centres (especially

with swimming pools)

Universities

In addition to these building types,

any mixed use development, such

as oces and retail, may also beeasible as, together, they provide

a constant heating demand.

The easibility o CHP or any

building relies on many actors

(see Building Evaluation); however,

a good heat baseload is usually

essential.

Micro CHPMicro CHP is a relatively new

technology that attempts to

service buildings with low heating

loads (

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KNOWLEDGE GUIDES

For Architects

XCO2 Energy 2009 www.xco2energy.com

London PlanThe London Plan provides an approach or reducing the operational carbon

emissions o new developments.

This is commonly known under the mantra Lean, Clean, Green, which

denotes the order o improvements to be made.

Lean - passive design energy eciency measures

Clean - CHP, Trigeneration and/or district heating networks

Green - Renewable energy technologies (biomass, wind, solar thermal, etc.)

Incorporating CHP or Trigeneration into a new development reduces the

quantity o renewable technology needed to meet the 20% target.

Depending on the type o development, the post-eciency CO2

emissions

can be reduced by 5 - 15%.

Trigeneration Trigeneration makes use o the

waste heat or cooling purposes.

An absorption chiller converts the

heat rom the CHP engine intochilled water.

Heat can be used or heating

purposes during the winter and,

with the application o the chiller,

can provide cooling during the

summer.

Because o this, Trigeneration can

result in much larger installations

than CHP providing much greater

environmental and nancial

benets.

Single, double and triple-stage

absorption chillers require dierent

temperatures to operate.

Most building-size applications will

use single-stage absorption chillers

which typically have a coecient

o perormance (COP) o 0.6 - 0.7.

Absorption chillers can require

signicant heat rejection

inrastructure and is likely to be

expensive.

Building EvaluationHeat and electricity demand

- Ideally the hourly heat and

electricity demand o the

development is required. However,in the case o new developments,

assumptions have to be made as

to the likely energy consumption

patterns throughout the year.

Space implications - CHP plant is

larger than typical boilers and will

require more plant space.

Fuel type - Certain gas pressures

are required and oil/biomass CHP

will require large storage space.

Noise implications - noise

attenuation may be needed and

noise levels in adjacent areas, air

inlets, exhaust outlets and nearbybuildings should be considered.

Vibration - anti-vibration mounting

o engine and pipework may be

required.

Stack height - special consideration

must be taken when speciying

exhaust gases and fue heights.

Location - CHP engines can be

situated in plant rooms, on roos

and externally in weather-proo

enclosures.

GlossaryCogeneration - CHP is sometimes reerred to as cogeneration.

Coecient o Perormance (COP) - A ratio o the heat energy extracted or

each unit o heat energy inputed. e.g. a COP o 0.6 means that or every unit

o heat supplied, 0.6 units o cooling is provided.

Heat-to-power ratio - The ratio o heat output to power output. e.g. an

engine that produces 100kW o heat and 50kW o power would have a ratio

o 2:1 (100/50). Micro CHP engines (domestic) typically have ratios o 3:1 -

15:1, small-scale systems (large buildings) have ratios o 2:1 and large systems

(district energy power stations) have ratios o 1:1.

Baseload - The minimum amount o heat or power required or a CHP engine

to be easible.

Modulation - The ability o an engine to work below ull capacity. Most

CHP engines can only modulate to approximately 75% o ull power beore

shutting down.

Load Profle - a graph showing a particular building load (e.g. heat)

throughout the year enabling a visual representation o the CHP operation.

This is usually an hourly prole.

CHCP/CCHP - Trigeneration is sometimes reered to as either Combined

Heat, Cooling and Power or Combined Cooling, Heat and Power.

Spark Gap - The dierence in price between a kWh o electricity and gas. The

wider the gap, the greater are the economic benets that can be obtained

rom CHP.

Climate Change Levy (CCL) - A levy imposed on electricity (0.456p/kWh)

and gas (0.159p/kWh). Certain CHP installations can be exempt rom this levy

(see Good Quality CHP) providing an additional economic incentive.

Good Quality CHP - Through a process known as CHP Quality Assurance,a CHP engine can be certied as Good Quality. Any CHP installation that

meets these requirements is exempt rom paying the CCL.

Integration with Renewable Technology

Photovoltaics

Very compatible

Any excess electricity can be

exported to the grid

Wind

Very compatible

Any excess electricity can be

exported to the grid

GSHP

Partially compatible

Shares some heat load

Biomass

Partially compatible

Shares some heat load

Solar Thermal

Generally not compatible

Removes heat baseload

required or CHP operation

Compatibility

Less More

CHP

XCO2 Energy ServicesWhen specied correctly, CHP can produce good carbon savings and provideshort payback periods o only ve to ten years.

Our services include:

CHP Sizing - Feasibility study or installing CHP in either new developmentsor retro-tting into existing buildings.

Site-wide Energy Strategies - CHP integration into large-scaledevelopments, energy networks and district heating.

Multi-Utility Service Company (MUSCo) Feasibility Studies - Investigationinto economic viability in terms o return on capital investiment or site-

wide services strategies.

Energy Statements - Local Authority planning application reportsconsidering energy eciency, clean technologies and renewabletechnology easibility.