A Data Center is a fairly unique type of building and presents a number of specific design challenges that must be addressed by the design team. The monthly energy bill for a Data Center is typically very high – close to the equivalent of that for an entire small city. This large energy consumption is due to the energy demands required to power the servers and associated equipment within the building.
The large equipment loads can also lead to significant cooling demands. By showing that the clients could maintain the design criteria in the Data Center for the servers to operate while minimising the need of mechanical cooling, significant energy savings can be demonstrated. IES Consulting contributed to significant cost and energy savings – approximately 40% on the space cooling energy loads through the simulation of various free cooling strategies.
The LEED Optimize Energy Performance credit allows design teams to achieve up to 18 LEED energy points by demonstrating the operational cost from running their Proposed design is less than that of a Baseline model. The number of points achievable are on a gradual scale where a 5% improvement is the minimum pre-requisite and a 50% reduction (for a New Construction) would achieve the maximum 18 points.
A further 1 point is available for innovation if the design exceeds a 54% improvement in energy efficiency over the Baseline. Therefore, LEED energy modelling is a key step toward achieving a Gold or Platinum rating – 33% of what is required for a Gold rating and 25% for Platinum. There are significantly more points available for this credit than under any other so it is imperative design teams carefully investigate how to maximise the potential credit return.
Unlike some other rating methods, the LEED energy model takes into consideration the whole building energy consumption, inclusive of uses such as equipment, lifts and escalators, car park ventilation, external lighting, kitchen, servers, etc.
Usually, non-regulated loads are treated identically between the Proposed and Baseline cases. This can present an issue in building types where these loads make up a significant proportion of the overall building energy.
This is indeed the case with a Data Center where the energy use associated with server equipment and associated loads could be in excess of 70% of the total building energy. Therefore, to meet even the mandatory 5% reduction, design teams would need to achieve a reduction of ~17% across all other energy uses.
The chart below illustrates the percentage reduction needed in the non-server equipment to achieve different number of LEED credits while keeping server equipment identical between the Proposed and Baseline case. This illustrates how difficult it is to achieve even a handful of LEED points for this credit. For example, in the case outlined below a design team would need to reduce non-server energy use by 47% to achieve just 5 LEED points for EA Credit 1 out of a possible 18 or 80% of non-server energy use to achieve 10 LEED points.
Happily, for Data Centers perusing LEED, there is an Alternative Compliance Path (ACP) that allows design teams to include the benefits from Low Energy Servers, Virtulization and efficient electrical system design. USGBC have produced a spreadsheet calculator in which the characteristics of the Data Center’s equipment can be described and it will then calculate an equivalent load for the Baseline case. This spreadsheet can be accessed from https://www.usgbc.org/resources/minimum-energy-performance-data-center-calculator.
With the increased server load in the Baseline case there is not only the increased energy cost associated with running the servers but also an increased load on the Baseline cooling plant, pumps and fans that will help when targeting increased energy cost savings.
When using the Alternative Compliance Path it is necessary to run further variations of the energy model, up to 5 model variants may be required. The LEED User manual describes these model variants as:
- Proposed model with full IT loading (normal Performance Rating Method model)
- Proposed model with initial IT loading
- ASHRAE model with full IT loading (normal PRM model)
- ASHRAE model with initial IT loading (optional)
- ASHRAE model with “baseline” IT loading (optional)
In addition to the two IT loading determined by the calculator (Variants 4 & 5), scenarios that report the performance under full IT loading and initial IT loading need to be developed. This considers that many Data Centers will not operate at full capacity until some point after commissioning. This also provides the option for the project team to be rewarded for minimising losses by using redundant equipment at part load during the initial IT loading. This is achieved by demonstrating the savings as an average between savings calculated from models 1 & 5 and from models 2 & 4.
Even when applying the Alternative Compliance Path, project teams still need to develop a Baseline energy model with identical IT loading as the Proposed case. This is because there is a requirement to demonstrate at least a 2% energy cost saving in the building systems independent of the IT loading and is achieved through comparing model variants 1 & 3.
Model variant 2 also serves the purpose to determine the Power Usage Effectiveness (PUE) of the Proposed case under initial loading.
While this Alternative Compliance Path can help to demonstrate significantly greater energy cost savings and unlock additional LEED Credits, it will require detailed information regarding the server equipment. It therefore drives a team approach through co-operation of the Data Center operator and the design team.
Data Centers present a unique set of design challenges, as the high internal IT load will require a significant amount of cooling to maintain the design conditions. Establishing ways of minimising this cooling load by exploiting ventilation free cooling options can help to significantly reduce the cooling energy and achieve additional LEED points. Dynamic simulation is the ideal tool to investigate design risk and demonstrate the effectiveness of design solutions across various climate zones.
Data Center cooling provision is dependent on the climate with cooler climates providing the opportunity to condition through natural ventilation, wet and dry fluid coolers and high efficiency systems when possible.
Another significant energy savings measure that the IES Consulting team modelled was the virtualisation of servers. Computers and servers within Data Centers make up 80-90% of the buildings energy, so the virtualisation contributes hugely to the energy savings.
IES have modelled Data Centers for a large number of high profile, global organisations, all of which have achieved or are on track to achieve LEED for New Construction (NC) Gold or Platinum ratings. We have enabled the projects to score very highly in LEED Energy points, with some gaining the maximum available. Take a look at our Data Center portfolio.