CHP, carbon abatement, and the future of the grid

By Ed Ansett & Gardson Githu
How a sustainable data centre design using CHP could set us on the right path for lowering emissions towards net zero carbon operations

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 abatement. 

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 ambitious. 

A 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 Center Design Using CHP will sets out how on-site energy production, harvesting, utilisation and heat recovery of data centre energy can, in appropriate circumstances achieve these aims. 

Global Context  

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 re-used. 

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 agricultural use. 

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 plants including a centrifugal chiller and cooling towers to reject the heat utilising a reversed Carnot cycle process. Typical cooling plants utilise water cooled chilled water plants with a centrifugal compressor, cooling towers and pumps. The range is 0.8 to 1.0 kilowatt per Ton of cooling.

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 homes. 

(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 grid infrastructure. 

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.

The third paper in the Data Center GHG Abatement series from EYP and i3 is titled Towards More Sustainable Data Center Design Using CHP and will be available to download soon, in the meantime please visit the i3 website to catch up on the previous white papers. 

About i3 Solutions Group 

i3 Solutions Group is a specialist data centre MEP consulting engineering firm. The company is globally recognized for its design expertise, future thinking and innovative approach exemplified by work such as Adaptable Redundant Power, High-Rise Green Data Centre, and the Singapore Government Green Data Centre Technology Roadmap. i3 Solutions Group provides mission critical design and consulting services across wholesale, colocation, cloud, telecom, financial and public sectors for data centre clients. 

About EYP Mission Critical Facilities Inc. 

EYP Mission Critical Facilities Inc., (EYPMCF) is a pioneering consultancy in the data centre and critical facilities industry with over two decades of experience assisting its clients plan, design, test and efficiently operate their facilities. With clients across many verticals, from enterprise to institutional, colocation and hyperscale, EYPMCF has unmatched experience and the capabilities to deliver projects of any size. With a global presence and projects in over 40 countries, it continues to drive new solutions and thought leading concepts to market that benefit its diverse customer base.


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