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Since 2001 our retrofit controls technology has been installed for improvements in efficiency in over 500 centrally heat European buildings. Developed from a dedicated 1M € EU funded R&D project, led by The Building Research Establishment (BRE) www.bre.co.uk , our unique algorithms have consistently optimised heating systems to save an average of 15% in energy and CO2 emissions. As a further development of the original R&D project, BRE and building scientists from Italy encrypted these algorithms into a retrofit boiler optimising controller, exclusively for exploitation by Fuelstretcher and a number of other collaborating European SME control suppliers.

The R&D agenda was driven by a consensus that all known Building Management System (BMS) , were limited in their application of building physics principles for optimisation of heating supply - at a significant cost in energy efficiency . These limitations still exist even with many new build and heating system refurbishment schemes. Unfortunately, our algorithms were not historically integrated into BMS. We have now addressed this and our FS HUB, as the key hardware platform for our Smart Heating Optimisation service, is capable of being integrated with the BMS through their specific network protocols.

The R&D Agenda

There are 3 fundamental principles, which underpinned the agenda of the R&D project. They focus on the importance of thermodynamics in the optimisation of central heating systems to enable quantifiable improvements in comfort and efficiency. They are as follows

  1. Boiler operating temperature set-points, even for the most efficient of boilers, should be adaptable, adjustable and automated within the BMS defined heating occupancy schedule.
  2. Boiler set-points must be calculated by profiling the dynamic flow of heat around the system i.e.
    • Primary Heat supplied by boiler(s) with circulating water as the heat transfer medium
    • Primary heat distributed & exchanged to meet BMS zone and local room comfort set-points
    • Heat internally absorbed by the building fabric and constantly dissipated to the outside.
  1. Our building scientists gave limited credence to the technique of comparing outside and inside air temperatures as means of developing optimal boiler operating set-points. Each building has a unique dynamic to produce heat, maintain it for comfort and mitigate its continuous loss by insulation to the outside during occupancy. The optimal dynamic resulting from this must therefore be profiled as a function of rates of heat transfer and not as simple spontaneous temperature differentials.

Therefore, for optimal efficiency and comfort, the heat supplied by boiler(s) needs to be managed by optimal water temperature set-points which adapt to the individual dynamic of the building.

Optimal Water Temperature (OWT)

Our scientists set out to develop a set of algorithms that would automatically calculate, develop and adjust boiler set-points to the Optimal Water Temperature (OWT) to satisfy the heating system’s thermodynamic profile. These algorithms are even more relevant today as more condensing type boilers are being installed in larger buildings. The full efficiency benefits of condensing boilers can only be achieved if heating system water temperatures are optimised.

Fuelstretcher algorithms are the only scientifically validated encrypted firmware available, anywhere in the world that automates the optimisation of water temperatures in central heating systems. Any heat produced by boiler(s), which is not optimal or perfectly balanced, is either wasteful or the building occupants will feel cold! It also has to contend with the fact that the average UK building fabric continuously loses, or its heating system wastes, 75% of the heat produced. Fuelstretcher’s Optimal Water Temperature technique (OWT) is now being applied to BMS networks to enable its benefits to be automated within the entire heating control systems of a wide range of buildings. OWT continuously adapts to suit the dynamics of heat supply and demand with no need for site programming or re-programming.

Key (OWT) Hardware

The Fuelstretcher Retrofit Controller is installed for optimisation of boilers by directly controlling them at OWT temperatures and where multiple boilers are installed, their sequencing. In its retrofit mode, whilst it interfaces with the BMS, it is not integrated with it or its network.

It also has no direct visibility of BMS comfort set-points to assess whether they are still performing correctly. Similarly it has to assume that that the BMS controlled valves and actuators, or Air Handling units, are operating optimally. In practice they often are not. Nevertheless the Fuelstretcher retrofit controller does take into account system water temperature feedback by the BMS to profile demand in order to optimise supply and save energy.

It is also a highly effective stand-alone heating boiler efficiency device. Therefore significant energy savings are achievable for buildings without BMS. Heating systems entirely served solely by Variable Temperature Circuits (Radiators) and condensing boilers will particularly benefit from the controller.

The FS HUB is Fuelstretcher’s web-based hardware platform at the centre of its Smart Optimisation programme. In larger buildings it integrates the OWT algorithms with the BMS network. In turn the FS HUB acquires data from the same network to enable Fuelstretcher to develop further optimisation strategies to embrace the entire heating system of controls and plant.

Impact of OWT on BMS Heating Management

The following graphics illustrate the effect that optimisation of boilers and their primary hot water temperatures have on a large commercial office where a Schneider BMS had already been installed.

Red graphs display key temperatures under BMS control before installation of Fuelstretcher control.
  • Primary Flow temperature (boilers) varies between 60 and 80 deg C during occupancy
  • Outside air temperatures during occupancy vary between 10 and 15 deg C
  • Room temperatures are maintained at 20/22 deg C to reflect acceptable comfort demand.
The Blue graphs show the result of installation of the Fuelstretcher controller.
  • Primary Flow temperature (boilers) reduced to between 50 and 60 degrees
  • Outside air temperatures are similar during occupancy at between 10 and 15 deg C
  • Room temperatures are maintained at 20/22 deg C to reflect acceptable comfort demand.
Conclusion The Fuelstretcher controller learns the dynamic of the system between 8 and 10am. As a consequence its OWT algorithms automatically calculate optimum primary circuit water temperatures to reduce primary circuit supply heat energy by 27% with no loss of comfort. OWT algorithms are now also encoded in our FS HUB for its integration with BMS and to enable Fuelstretcher’s Bureau to remotely monitor and improve BMS and plant performance. The combined effect of OWT and Smart Optimisation techniques are planned to save 20-25% in total system energy.

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