Digitising HVAC design to achieve net zero

from Campus Estate Management Magazine Autumn 2020

How digital twins can dramatically reduce heating and cooling energy costs and carbon emissions, by Chris Davis, Hysopt

Low carbon recovery

Back in July, the Committee on Climate Change (CCC) said that the Government must seize the opportunity to turn the economic recovery from the Covid-19 crisis into a defining moment in the fight against climate change.

The energy systems owned and operated by universities are comparable in scale and complexity to many UK towns; and as a sector, consumption of gas and electricity - along with associated carbon emissions – are on an industrial scale. Within this, the challenge to decarbonise heating and cooling is a perennial and increasingly urgent issue. According to data released by HESA(1) (higher education statistics agency) around 60% of energy use in university campus estates is for the production of heating and hot water.

Energy challenges

The past 6 months of course have been a tumultuous time for universities, not least for the many energy managers that we’ve spoken with during this time. The broader questions over if, when and how life might return to university campuses are now starting to be answered; however from an energy point of view, common feedback includes:

• Energy consumption and savings during the lock-down period reduced somewhat, but not as much as might have been expected;

• Moving forwards – for the short term at least - the way in which estates buildings will be used will change significantly (less buildings occupied than normal, but with longer hours of daily operation);

• New guidance from CIBSE on safe ventilation of buildings (higher air change rates and no heat recovery from exhaust air) will come at the cost of energy saving and carbon emissions reduction;

At the same time, UK universities are in the vanguard of the drive towards net-zero carbon, with at least 19 universities having declared climate emergencies(2), and with many having set themselves challenging targets to achieve Net Zero Carbon, some by as soon as 2030.

With a seeming conflict between short-term operational vs long term strategic challenges in mind, how can digitisation of HVAC systems help universities tackle decarbonisation and energy costs across their estates?

What is a digital twin?

A digital twin is a virtual replica of something physical – be it an asset, product, or system. The technology helps create an interface that bridges the digital and physical worlds, for example in construction and building management. Digital twins enable designers and building managers to “predict the future” of their installation – and to bring transparency to help answer difficult questions that might otherwise rely on assumptions or rules of thumb.

In the case of heating and cooling installations and district heating networks, HVAC digital twins are able to provide university estates professionals with a much clearer understanding of how their systems will perform. This can answer questions such as:

• why existing installations are not performing as well as expected from an energy cost, carbon emissions, or thermal comfort point of view; or

• how the deployment of new low carbon heating and cooling technologies might be designed for optimal trade-off between operational cost; best-value upfront investment cost; or lowest carbon emissions.

What’s wrong with the traditional approach to HVAC design?

Traditional approaches to HVAC system design tend to be based on so-called peak load calculations – i.e. does the planned installation meet the required heating/cooling load under a set design condition (e.g. -5°C outside temperature)?

However, for 99% of the year, installations don’t operate at these “full load” conditions. This is where HVAC digital twins bring real value, as by applying criteria such as building energy load profiles, weather data and control strategies the digital model has the ability to dynamically simulate the behaviour of systems under continually variable “part-load” conditions – along with the impacts these have on costs, carbon emissions and comfort levels.

And for schemes aiming to achieve low-zero carbon emissions, transparency over this part-load behaviour is crucial. Poor system design, based on rules of thumb; peak load performance; and component (rather than system) behaviour can lead to systems which ultimately:

• Cost too much to run;

• Cost too much to install;

• Don’t deliver expected carbon savings;

• Fail to deliver adequate thermal comfort

The role for digital twins in campus estate management

In brief, HVAC digital models bring a number of opportunities to help tackle both the short term and longer term issues university estates are facing today:

Short term

HVAC digital twins bring transparency over operation and performance of existing heating and cooling installations, allowing them to be optimised for lower energy consumption, typically resulting in annual energy cost savings between 20-50%. Low investment costs due to identifying “quick wins” offers paybacks typically in 1-3 years.

This is very often the case where CHP has already been installed, but poor design, integration and control means the energy saving potential of the technology is not being maximised. Or in the case of heat pump installations where the predicted returns from Renewable Heat Incentive are not being achieved.

Medium term

Universities are already adopting polices to replace end-of life gas boilers with low carbon technologies such as air source heat pumps. While heat pumps have the potential to deliver immediate carbon emission savings, they are not a like-for-like replacement for gas boilers. Modelling the optimal way for deployment by considering the impacts and performance of the wider system, as well as the correct hydraulic integration and control strategy helps the right choices to be made early in the project.

Long term

Universities with district heating networks are investigating how best to decarbonise these, potentially by moving away from fossil fuels. Hysopt is already working with several UK universities to build digital twins of existing district heating networks – complete with full hydraulic models of the buildings connected to them – to help establish the potential for entire systems to operate at lower temperatures and therefore increase the scope for lower temperature heat generation sources, such as heat pumps or heat from waste.

Campus development

In new builds, optimal integration of modern, efficient heating/cooling technologies is key to delivering sustainable buildings, that are both energy-efficient in operation and comfortable to work in. A digital twin can go through thousands of changes before it is finalised and used to construct its physical twin. Eliminating the common design error of over-sizing reduces upfront capex costs; while automated component selection and commissioning optimisation means “first-time right” operation at hand over.

Digital Twins vs BIM

We’re often asked the difference between an HVAC digital twin and the Building Information Models (BIM) already produced for new buildings.

Simply put, BIM models generate and manage digital reproductions of the components that are in a system design and provide visibility of how an installation will “look”. Digital twins meanwhile are unique in that they simulate the dynamic behaviour of an installation and provide key data and metrics relating to how it will “perform”.

Moreover, designing HVAC systems using digital twins allows

engineers to experiment with different system concepts and evaluate these against one another before committing to a final design.

Key performance metrics such as annual energy consumption, energy cost, CO2 emissions and even thermal comfort are all reported as measurable outputs from the digital twin, allowing building owners to understand the answers to a range of “what if” scenarios and build solid business cases based on fact-based analysis to support decision making in the trade off between capex, opex and environmental objectives.

Other benefits

Running simulations on a digital twin also reduces risk, helping building managers to make better business cases for system changes. By experimenting on a digital twin, equipment performance (boilers, CHP’s, heat pumps) can be improved, just one way in which digital twins drive cost-efficiency.

Cost reduction is also a major application of digital twins: by bringing transparency over how a system will perform and removing Kas Mohammed the need to include margins for error to cover estimates or unknowns, upfront capital investment cost savings on HVAC plant, installation and commissioning can be reduced by as much as 15%.

As-designed = As-built

A further advantage for HVAC digital twins is the ability to help ensure that design intent is successfully translated into the as built installation. Traditional approaches to heating and cooling system design might secure energy efficiency in theory, but rarely in practice, leading to the well-known ‘performance gap’ that exists between original design intent and how a building truly performs in-use.

HVAC digital twins help resolve this problem, firstly by calculating precisely the correct sizing and selection of individual components for lowest energy use/carbon emissions - for example pumps, control valves, balancing valves; and secondly by ensuring that this information is shared with installers, along with details of how each of these components should be correctly commissioned. This both reduces cost and risk for the building owner and installer by speeding up the commissioning process; significantly increasing the chances of a “first time right” installation; and reducing the time and costs associated with correcting defects after hand-over.

The digital models created are also a shareable asset, so can travel with a project from inception through to completion and be continually evolved during the course of a project by different stakeholders. This provides continuity through all key project stages, as well as providing a full digital dossier of the final as-built installation, detailing not only what is being handed over, but also how it performs.

Digital Twins in action

Hysopt digital twin software has been used to help reduce energy and plan new HVAC installations with universities in Europe for over 8 years and in the UK since 2018.

Once such example is KU Leuven, the largest university in Belgium. “We have very old buildings and are committed to making them more efficient, which is a very big challenge,’ explains Bert Vandeborght, Head of the HVAC Project Office, KU Leuven. ‘We are involved in Leuven Climate Neutral 2030 and want to play a leading role in this as a university.”

“We build new construction projects fossil-free, no question. In existing buildings or boiler rooms that are being renovated, we aim to cover about 80% of heat fossil-free.”

“An important advantage of the Hysopt digital twin for us is the fact that it helps us quantify the saving potential of hydraulically optimised installations. We can also take on the challenge of designing and validating hybrid installations of boiler rooms with boilers and heat pumps. We see our continued collaboration with Hysopt as something that will allow us to optimise the various buildings further over the coming years.”

Implementing a digital twin to innovate

If implemented correctly, digital twin technologies can have a major impact on building management and operations. Across the entire value chain, a digital twin enables the right decisions to be made; while protecting the integrity of the design in the final installation.

The design of today’s low energy, low carbon heating and cooling systems are too complicated to design without specialist simulation and optimisation software – meaning that digital twin technology is a must. Put simply, a modern low carbon building cannot hope to provide low-zero carbon heating and cooling without a digital twin.