Embodied energy or Emergy is an accounting methodology which aims to find the sum total of the energy necessary for an entire product life cycle. If we look at the ‘product’ data center we can say that it is basically a value stack. A supply chain of stack elements who act as a service component. People, Process and IT that adds up to an IT service component. (Check out the Data Center Pulse Stack at Data Center Pulse for more thoughts on treating the data center as a stack.) A data center has from an energy perspective a supply chain that consist of four large building blocks: the IT infrastructure (servers, storage and network) for processing workload, the primary power supply (UPS, PDU, etc.), the secondary support supply (cooling, generator, air handling) and the tertiary support supply (lighting, office space). To manage the energy usage of this data center stack effectively and efficiently, it needs not only to be treated as a system but also the life cycle must be taken into account. There is an initial investments of energy in the construction of the data center. The data center then produce energy for a number of years, to process an amount of workload, until it reaches the end of its effective lifetime. Along the way, additional energy costs are incurred in the operation and maintenance of the data center. And after the end of its effective lifetime there is an investments of energy in the disassembly of the data center. For the data center life cycle we thus can define three phases (see figure):
- pre-production; the construction of the data center facility (raw material extraction, transport, manufacture, assembly, installation)
- production; utilization of the data center facility (data processing and data storage as primary process and supplementary processes)
- post-production; the breaking up of the data center facility (disassembly, deconstruction and/or decomposition)
DC Energy Life Cycle
During production the primary power supply is directly delivering energy to the IT infrastructure, the rest of the power supply is supporting. A further process analysis of each phase in the data center life cycle can give more detailed information on the energy cost of a data center and can lead to an Energy Cost Accounting System
DC Cumulative Energy Life Cycle
If we see energy efficiency as a topic that has something to do about sustainability than sooner or later you are confronted with words like exergy and emergy. Energy is a word we all know and it means the ability to cause work were work is defined as any useful energy transformation. In all kinds of work, one type of energy is transformed into another where some of the energy going into a used form that no longer has potential for further work.
Not all forms of energy are equivalent. While they can all be converted to heat one cannot say that joules of one form of energy are equal to joules of another form in their ability to cause work. This concept of quality required a new concept of energy. Exergy quantifies the useful work that may be done by a certain quantity of energy. But energy has also another aspect, it has a history. Embodied energy or Emergy is defined as the available energy that was used in the work of making a product. Embodied energy is an accounting methodology which aims to find the sum total of the energy necessary for an entire product lifecycle: raw material extraction, transport, manufacture, assembly, installation, disassembly, deconstruction and/or decomposition.
In this energy transformation chain at each transformation step some energy is degraded and some is passed to the next step in the chain. The emergy of one type required to make a unit of energy of another type is called transformity. These Energy Transformation chains can be described with the help of the Energy Systems Language (ESL) of Howard Thomas Odum. See Emergystems.org. A simple example of data center energy chain presented as an ESL diagram is given below.
An ESL example
Emergy aims to provide an ecocentric value of industrial products and processes instead of the economic value, which is anthropocentric. Emergy analysis claims to provide a more holistic alternative to many existing methods for environmentally conscious decision-making. All though there is still discussion about the practical usefulness of emergy in an engineering environment if you want to make some effort on sustainability it is worthwhile to spend some time on it. There is a very nice EMERGY SIMULATOR available. This Java application is written by Raphael Valyi and you can find and download it on Sourceforge
So the new question can be what is your data center emergy. Enjoy your new sustainability project!