An energy flow chart for energy use in the residential building sector is shown on the Autodesk Sustainability Workshop page ‘Measuring Building Energy Use’. There is also a similar Sankey diagram for energy sources consumption in the commercial building sector.

Both are taken from a Pacific Northwest National Laboratory (PNNL) report from 2006 prepared for Department of Energy (DOE) titled ‘Energy End-Use Flow Maps for the Buildings Sector by D.B. Belzer (PNNL-16263).

Residential building sector energy flow chart:

Commercial building sector energy flow chart:

Both Sankey diagrams are built up the same way. The top part of each diagram shows electricity generation, the bottom part the energy flows for heating. Significant conversion and transmission losses can be identified by the arrow branching out at the top. Flows from the left represent the energy sources: coal (brown), natural gas (blue), biomass/solar (green). To the right the flows are broken down to the individual consumption, such as heating, cooling, lighting, other electric appliances, etc.

All units are in quadrillion BTUs for the U.S in 2004.

This article on ‘A Pilot for Measuring Energy Retrofits’ describes how researchers from the EEB Hub used an old navy building in Philadalphia to “determine detailed system performance”.

EEB Hub researchers outfitted Building 101 with sensors and a data acquisition system to determine detailed system performance, building energy loads, indoor environmental quality (IEQ), and a detailed operation of the building control system. … The sensors read data from 509 sensing points, collecting 1,048 pieces of data at one-minute intervals. These data points track indoor air quality, occupant comfort, and building energy use.

The result of that “inverse modelling” (i.e. measuring) approach are presented in Sankey diagrams and are used “to identify discrepancies in the predicted versus actual energy balance”.

There are significant differences between the January energy use…

… and the energy picture in July

While in winter mainly natural gas is used for heating, the gas consumption in summer is down. In July electricity consumption is significantly higher due to air conditioning.

Unfortunately no unit of measurement is given (it could be kWh), but nevertheless proportions of the energy flows are correct.

Read full article.

Architect Ziya Buluch has a comprehensive description of his project ‘The Nest’ on his blog. The Nest is a green building which is planned to have no external primary head demand.

Scroll down to the end to find this Sankey diagram:

The flows represent the heat energy. Overall demand for heat 37.46 kWh per square meter per year. 12.08 kWh/m2a is from solar panels, 25.38 kWh/m2a from an air-source heat pump (whaterver that is…).

Untypical Sankey diagram, but nevertheless interesting. Flows are not really to scale (compare the 12 kWh inflow and the 6 kWh losses outflow, which should have half the width, or to the 25 kWh inflow that should be roughly twice as wide). Unicolor grey flows with a slight gradient from left to right.

Found this via utsapocalypse. The Sankey diagram is originally from the article ‘Preliminary Investigation of the Use of Sankey Diagrams to Enhance Building Performance Simulation-Supported Design’ by William (Liam) O’Brien of Carleton University, Ottawa.

The paper proposes “the outline for a methodology for creating Sankey diagrams to represent energy flows in buildings, with the eventual intent that the methodology be integrated into a software tool.”

The Sankey diagram shows the energy balance of a house for a mid-winter week. Flows are in kWh, total amount 804 kWh. Energy sources/types are from the left (purchased heat, domestic hot water, solar gains), energy consumption and losses to the right (heat loss through windows, ceilings, walls).

Plenty of colors used in the diagram, Sankey arrows glued together from shapes. As the author mentions “the underlying creation process, when performed manually, can be quite complex”.

Premnath Sundharam from the Visualize Green blog contacted me to draw attention to a Sankey diagram template he has made and that is available for download on his site.

The diagram is for predicted energy intensity for buildings. An Excel template is provided that allows entering the data. You can use this with the free trial version of e!Sankey (registering required). All elements of the diagram and the entry sheet is explained in detail by Premnath. In regard to the unit (KBtu per square foot per year) he says:

Last but not least, kBtu/sf/yr is becoming the universal (US) unit of communicating building energy consumption. This unit is called the EUI – Energy Use Intensity and since it is a simulation of how your building will perform, it is called PEUI – Predicted Energy Use Intenisty.

Good stuff, Premnath! Thanks for making this available to everyone.

Note November 2011: Also look at Premnath’s Energy Story here.

This website on energy optimized building features a case study of a students dorm building at Wuppertal, Germany. [On a side note: it is quite striking that when I browse for new Sankey diagrams on the web, I come across them on German websites. Herr Sankey could well have been a German...]

The two Sankey diagrams shown along with the article visualize the heat energy flows before and after the optimization measures taken.

before:

after:

Flows are in kWh per square metre per year. The first diagram breaks down heat consumption into heat used for room heating and for warm water preparation. In the second a new heating system has been installed providing heat mostly over the air circulation system. Only some static radiators remain. [Thanks Thomas for helping me with the translation/explanation].

Apart from the use of a fancy color, the Sankey diagrams are well done and comprehensible. Flows are to scale.