With the help of IES, Barts Health NHS Trust has been able to understand the likely impact of a range of energy conservation measures at the Royal London Hospital in Whitechapel
The largest NHS Trust in the UK, Barts Health NHS has set itself the goal of being the country’s most sustainable NHS Trust by 2020, too.
During 2016, it undertook an innovative project with 3D performance analysis software specialist IES on enhanced energy modelling and building management systems (BMS) data analysis for the Alex Wing dental teaching hospital at the Royal London Hospital in Whitechapel.
The IEC Ci2 consulting team produced a calibrated model of the Alex Wing building, by using existing building performance data and the IES SCAN web portal. This enabled the success of energy conservation strategies to be measured and will allow new strategies to be evaluated in future.
The programme was delivered in conjunction with Skanska and took advantage of the Alex Wing’s existing BMS and extensive sub-metering infrastructure, with the goal of improving how the Trust approaches assessment of proposed energy conservation measures, or ECMs.
Using a combination of building data and advanced computer modelling, IES was able to create a virtual benchmark for the building which comfortably meets the calibration thresholds for ASHRAE Guideline 14. It calibrated the model down to monthly levels on the gas side (where only daily readings are available) and to hourly levels for electricity.
Online and offline sources
One of the biggest challenges lay in pulling together data from a number of online and offline sources, in order to build the initial simulation model of the building, enhance it and finally calibrate it, by matching simulation data against real data for a benchmark period of April to December 2015.
Design, post-build and operational data needed to be pulled together, all in different formats, resolutions and time-steps. Information variously came from geometry data in Navisworks files, building log books, PDF documents detailing thermal properties, BMS and AMR (automatic meter reading) data, manual reads, and much more.
IES provided visibility of existing building performance time-series data, consolidating AMR, BMS and condition data using the IES SCAN web portal. This included a range of data such as energy, plant operation, and indoor environmental conditions. Hourly weather data to support heating degree day (HDD) and cooling degree day (CDD) calculations and building energy simulations was also sourced by IES.
The extensive sub-metering available at the Alex Wing facilitated in-depth analysis of energy use breakdown at the site. By utilising real-year historical weather data in the simulation, it was possible to provide a better match of model-predicted energy use against historical energy use.
However, even with such extensive data, calibration can be challenging, due to uncertainty caused by malfunctioning meters, data loss and the inherent difficulty of extrapolating energy use from pulsed meter readings.
The final calibrated benchmark model that IES created has been used to successfully identify operational issues, act as independent validation of the energy savings impacts being achieved through a separate ongoing commissioning project, and virtually evaluate the effectiveness of proposed ECMs.
A series of measures were reviewed by IES in the calibrated benchmark model in four different stages. The data analysis and modelling presented a number of ECMs; if all were implemented, it was determined, a 22.5% reduction in gas energy demand and a 30% reduction in electricity energy demand could be achieved.
This equates to a 28% reduction in energy spend and a 27% reduction in carbon dioxide emissions.
The measures reviewed were:
• Changes to controls strategies.
• Changes to plant operation schedules and the addition of AHU fan inverters.
• Installation of Solar PV and CHP (combined heat and power systems).
• All of the above.
The figures produced enabled Barts to see the effect of different groups of measures in isolation and in accumulation.
Work underway Changes to control strategies have already been implemented at the Alex Wing, through a separate commissioning project. The savings predicted by IES are in line with the savings that the on-site commissioning team is tracking in real life.
IES claims that one of the key advantages of its Ci2 service is that, by looking at measures in isolation and in combination, clients get new perspectives on the relative impact of measures. In this way, they are better equipped to make business- led decisions.
For example, when the CHP system was introduced, an increase in gas energy demand was observed, against a significant reduction in electricity energy demand. However, IES was able to put this into context by also looking at the associated reductions in energy spend and CO2 emissions that this change would lead to – both in isolation and in combination with other measures.
To complete the project, IES has now handed the calibrated model of the building to Skanska, so that its team can use this valuable digital asset in future work. Training has also been undertaken to enable Skanska staff to utilise the model in evaluation of future proposed energy conservation measures, changes in use, refurbishment, and in continuous commissioning of the building.
The main advantage of this approach is that measures can be considered in combination rather than separately, taking into account interactions and knock-on effects that might occur, and enabling quick virtual testing of different combinations.
Other advantages include the ability to evaluate measures from a business case perspective, predicting improvements in cost, energy and environmental conditions that can be linked to payback periods and other metrics in order to make strategic decisions.
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