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Introduction
Site
Building
Photovoltaics
Solar Water
Wind
Summary
Energy
Economics
Summary
Indicators What are these indicators?
   
Energy consumption 
Embodied energy 
Energy bills 
Construction cost 
 
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Renewable Energy and Buildings

This tool allows you to investigate renewable energy strategies for a proposed or existing building. It is designed to interactively explore different options at an early stage in the design process.

A basic configuration of site, building and renewable systems can be chosen using the pull down menus of standard options and the simple entry fields, all of which are shown in pale green. The numerical values used in the estimates are shown in the orange boxes and are updated depending on your choices. If you wish to hone your estimates then you can adjust these values. Each section has an link providing further information. The pane to the right indicates the effect of renewable energy systems on your building's energy consumption, bills, embodied energy and construction cost.

In addition to estimating costs and reductions in primary energy use, the tool allows you to take account of the embodied energy of the renewable systems and of any components which they might replace. Ideally we should also consider the overall effect of the strategy on energy use - does the facade reduce thermal performance leading to higher heating loads? Is the form of the building when the facade is incorporated less easy to naturally light or ventilate? These issues are not tackled as they require far more detailed modelling.

Martin Centre logo This project was funded by the Cambridge-MIT Institute and carried out by Jonathan Woolf at the Martin Centre for Architectural Research at the University of Cambridge, UK between November 2001 and August 2002.

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Site and Terrain Effect of terrain on wind power
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The amount of wind energy on a site depends not only upon its geographic location but on the surrounding terrain.

Mean wind speed m/s
Solar energy to kWh / m2 yr
Wind energy to kWh / m2 yr
Building Information Energy consumption and building type

Select a building type and floor area below. This gives a baseline energy use, construction cost and embodied energy which are then modified by the addition of renewable energy systems.

with treated floor area m2

Electricity demand kWh / m2 yr      Construction cost / m2
Space heating demand kWh / m2 yr Embodied energy kWh / m2
Water heating demand kWh / m2 yrLifetime years
Further data
The data below is used in the calculations. Please adjust the figures if they are incorrect for your design.
NB: the tool assumes that the same price is paid for any surplus electricity exported to the grid as charged for grid electricity. Since there is no calculation of load matching it is impossible to accurately estimate the cost implications of different prices.
 
Primary energy efficiency of grid electricity %      Cost of grid electricity / kWh
Primary energy efficiency of water heating fuel % Cost of water heating fuel / kWh
System efficiency of water heater %   
Photovoltaic installation Photovoltaics
with area of m2
System efficiency % Lifetime years
Installed cost / m2      Embodied energy kWh / m2
Orientation and overshadowing Photovoltaics and overshadowing

Click to set the appropriate orientation (radial lines) and tilt (semi-circles) of your photovoltaic array Click to set the appropriate orientation (radial lines) and tilt (semi-circles) of your photovoltaic array Click to set the appropriate orientation (radial lines) and tilt (semi-circles) of your photovoltaic array Click to set the appropriate orientation (radial lines) and tilt (semi-circles) of your photovoltaic array
     

Mean horizon angle degrees

What do the photovoltaics replace? Integrating photovoltaics

Lifetime years      Embodied energy kWh / m2      Installed cost / m2   

Solar collectors Solar water heating

with area of m2

System efficiency% Lifetimeyears
Installed cost / m2     Embodied energy kWh / m2
Orientation and overshadowing Solar water heating and overshadowing

Click to set the orientation (radial lines) and tilt (semi-circles) of your solar collectors Click to set the orientation (radial lines) and tilt (semi-circles) of your solar collectors Click to set the orientation (radial lines) and tilt (semi-circles) of your solar collectors Click to set the orientation (radial lines) and tilt (semi-circles) of your solar collectors
    

Mean horizon angle degrees

What do the solar collectors replace? Integrating solar water heating

Lifetime years     Embodied energy kWh / m2      Installed cost / m2   
Wind Power Wind turbines

rotors in an array with machine(s).

Diameter m Installed cost / turbine
Rated power kW      Embodied energy MWh
System efficiency % Lifetime years
Height of the turbine Effect of hub height on wind power

Wind turbines are sensitive to the surrounding terrain and to obstructions to the smooth flow of wind. The higher the turbine the less effected it is and the greater the output. Small turbines should be mounted as high as possible and large turbines usually have a tower roughly as tall as the blade diameter.

Height of the wind turbine hub above ground m

The building with renewables and without

All estimates shown to 2 significant figures.

 With renewable energy systemsWithout renewable energy systems
Annual grid electricity
consumption per m2
Annual gas/oil
consumption per m2
Annual primary energy1
consumption per m2
Embodied energy2 per m2 per year
Annual energy bill per m2
Construction cost per m2

1The primary energy consumption of the building. This takes into account the efficiency of conversion of energy at each stage in the process from source to supply. For example, each delivered kilowatt-hour of mains electricity in Britain corresponds to around 3.6 KWh of primary energy (mostly in the form of fossil fuels). Primary energy is a good indicator of carbon dioxide emissions and of other environmental concerns.

2The embodied energy of the building. This takes into account the energy required to manufacture, transport and install all the components of the building. The figure shown is a per year figure divided by lifetime i.e. the embodied energy of each component is divided by its lifetime to provide comparison between components with differing lifespans.

Energy breakdown

All estimates shown to 2 significant figures.

 PhotovoltaicsWind turbinesSolar water heating
Annual energy generation
Generation as % of demand3
Annual reduction in
primary energy use4
Reduction as % of
building consumption5
Embodied energy (per year) of
renewable components6
Embodied energy (per year) of
replaced components7
Net embodied energy (per year)8
Energy payback as % of
renewable's lifetime9

3Photovoltaic and wind turbine output is shown as a percentage of the building's electricity consumption and solar water heating as a percentage of the energy demand for hot water.

4This row shows the contribution of each renewable in reducing the primary energy consumption of the building. Photovoltaics and wind power, which substitute for relatively inefficient electricity generation, have a larger impact per generated unit than solar water heating.

5The contribution of each renewable is shown as a percentage of the annual primary energy consumption of the building without any renewable systems.

6The embodied energy of each renewable energy system. The figure shown is normalised by lifetime i.e. the total embodied energy is divided by the lifetime in years to allow comparison between systems with different lifetimes.

7The embodied energy (divided by lifetime) of any components replaced by either photovoltaics or solar water heating panels is shown in this row.

8The net embodied energy is the embodied energy of the renewable components less that of the components they replace, again divided by the respective lifetimes.

9The percentage of the lifetime of the renewable system required to generate the associated net embodied energy.

Financial breakdown

All estimates shown to 2 significant figures.

 PhotovoltaicsWind turbinesSolar water heating
Annual revenue
Revenue as % of bills10
Installation cost of
renewable systems
Installation cost of
replaced components
Net cost
Simple payback period
(no interest calculated)
Payback as % of
renewable's lifetime

10The revenue from each renewable is shown as a percentage of the relevant annual energy bill (i.e. electricity for photovoltaics and wind turbines, and gas or oil for solar water heating) for the building without any renewable contributions.

Energy breakdown
 
Photovoltaics
Wind Turbines
Solar Water Heating
 
 
 
 
 
 
 
 
 
 
 
Primary energy saved per year * 
Embodied energy (per year of lifetime)** 

*Lighter colour represents the range of estimates.

** Lighter colour represents the difference between the embodied energy of the renewable system and the net embodied energy (where we subtract the embodied energy of any components the renewable replaces e.g. photovoltaics might replace roofing). The embodied energy of each component is divided by its lifetime to give a per year figure.

Financial breakdown
 
Photovoltaics
Wind Turbines
Solar Water Heating
Lifetime energy bills saved * 
Installation cost ** 

*Lighter colour represents the range of estimates.

** Lighter colour represents the difference between the installation cost of the renewable system and the net installation cost (where we subtract the cost of any components the renewable replaces e.g. photovoltaics might replace roofing).

 
 
 
 
 
 
 
 
 
 
 
Summary: building energy use and bills
 
Building without
renewables
Building with
renewables
Primary energy for electricity / year* 
Primary energy for space heating / year * 
Primary energy for water heating / year* 

*Lighter colour indicates the range of estimates.

 
 
 
 
 
 
 
 
Building without
renewables
Building with
renewables
Annual bill for electricity* 
Annual bill for space heating * 
Annual bill for water heating* 

*Lighter colour indicates the range of estimates.