Global climatic change means that for
every part of the power chain from generation, across the grid and for
intensive energy users such as data centres, the name of the game is carbon
A response is needed from the data centre sector. This must align with where data centres of the future will be located – e.g., in data centre parks or within industry campuses. It must also encapsulate how their operation will be integrated with local, metro and national power, heating and cooling infrastructure.
From a data centre
perspective, the changes happening in upstream power can appear chaotic. The
first question to be raised is: “Can the
data centre play a role in reducing its own carbon footprint while supporting
greenhouse gas abatement of the grid itself?”
That alone sounds
second consideration is that as well as bringing benefits to the grid, future
designs may well have to provide carbon-free cooling and heating for a
surrounding campus or to the local public or privately owned built environment.
Yet more complexity
arises because data centre operators have their own priorities. Any improvements to
the whole power chain and use of cooling and heat must be achieved using
existing energy sector technology while improving, or at least maintaining, on-site
power reliability and reducing GHG emissions.
The third paper in a series from the EYPMCF and i3 Solutions and GHG Abatement Group, Towards More Sustainable Data Centre Design Using CHP will set out how on-site energy production, harvesting, utilisation and heat recovery of data centre energy can, in appropriate circumstances achieve these aims.
Current and future data centre space,
power and cooling demands present the industry with new challenges.
Fundamentally the challenge is the need for
on-site embedded power generation, based on a sustainable design with a low carbon
footprint. Such challenges call for new ways of designing data centres.
One proposed solution is an innovative
approach built around Combined Heat and Power (CHP) which includes a list of
considerations encompassing decentralisation of energy production, use of
renewable energy, small scale energy production (Microgrid), improvement of
energy usage and power distribution efficiencies, how power at the site is
generated and used, together with how the waste heat harvested on-site is
The benefits of a design that involves the
use of CHP production at the site of the end-user eliminates power transmission
losses and enables the capture of heat from the exhaust of a gas turbine, so improving
the overall efficiency of the power production process.
Installing co-generation plant at the site will provide
all required power, as well as cooling. Also, heating for nearby campus buildings or
This can be achieved because within the data centre
itself, power reliability can be improved by multiple on-site power generations
sources. The use of natural gas in such a design creates an added environmental
benefit in that NOx, SOx and particulate production is reduced
dependent upon the overall grid fuel mix emission factor.
Case study – how CHP can work to lower
data center emissions
There follows a sample study of a data centre with an
assumed IT power capacity of 10MW (overall electrical capacity of 11.48MW) and
associated cooling demand of 3000-Ton (10.5 MW). A typical installation would
include three (3) turbine engines in an (N+1) redundant configuration. All
mechanical cooling equipment is also configured in an (N+1) redundant configuration.
Turbine exhaust gas temperature ranges from approximately
340°C to 540°C. Exhaust gases are diverted through a heat exchanger to produce
steam which is used in an absorption chiller to produce chilled water.
Two (2) 5-megawatt gas turbines have a cumulative exhaust
gas flow rate of approximately 150,000 lb/hr., – sufficient to produce over
7000-Ton of cooling (24.6 MW).
In the example, an absorption chiller
replaces traditional cooling plant including a centrifugal chiller and cooling
towers to reject the heat utilising a reversed Carnot cycle process. Typical
cooling plant utilises water cooled chilled water plant with a centrifugal
compressor, cooling towers and pumps. The range is 0.8 to 1.0 kilowatt per Ton
For a typical 1.0 kilowatt per Ton centrifugal chiller
plant, energy usage is approximately 3MW, leading to total site energy usage of
13MW (i.e., IT load plus mechanical load). By comparison, the use of an absorption
chiller frees 3MW of power, which is available to provide relief on the
electric grid and reduce the overall energy consumption of the facility.
Such a design cuts the carbon footprint of a 11.48MW
total connected load data centre by 50%, while fuel consumption is reduced by
553,431 MMBtu. The subsequent reduction in carbon emissions is equivalent to
total annual greenhouse gas emissions generated by, e.g., 20,258 cars or 10,818
(A detailed case study, complete with graphics and
calculations of stream output estimates, overall CHP Thermal Performance, Electricity
profiles, Overall benefits of Co-generation power and cooling Plant and an
Emissions Summary table is available within the Whitepaper.)
As noted above, a global response to a global problem is needed. A
single solution will not fit all circumstances. However, many of the problems
to be faced are common to different geographies.
Depending on existing national power strategies and fuel mix,
different locations have different dependencies. Countries with easy access to
and a high dependency on e.g., coal, may have low-cost power but high kgCO2e/kWh.
Some countries, such as Poland, China and Germany already face criticism from
environmental activists for their continued use of coal power. In all
territories, whether in advanced or developing economies, how CHP for data
centres is deployed must not add to the total or marginal emissions of changing
Between now and 2030, how such grids decarbonise may dictate the
adoption rate of CHP based on its carbon footprint and return on investment. Nonetheless,
the time to consider CHP as one design option is now.
By Ed Ansett, Chairman at i3 Solutions Group and Gardson Githu, Senior Mechanical Engineer at EYP Mission Critical Facilities, Inc.