Heat Network Optimisation

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Key Points

  • Heat network optimisation varies from simple HIU (re)commissioning to a full redesign of a complex energy centre.
  • Most networks have problems from end-to-end. TRVs to boilers.
  • Optimising plantrooms is as important as optimising networks.
  • It is an error to think obtaining <35C return temperatures following optimisation will (1) last for long, (2) translate to improved heat generator efficiency and carbon savings
  • BMS control systems are sub-standard. They prevent operational feedback into design, which is critical to improve. They are designed to control the flow of money rather than water.
  • BMS data is every 15 minutes as standard - useless for fault finding.
  • Designers do not check the details of control systems such as PID loops prior to handover.

Links

Introduction

Heat network optimisation is the term used for fixing sub-standard communal heating and hot water systems.

We have suffered decades of erroneous guidance, a complete lack of regulation, and a systemic refusal to look at operational data until recently.

Heat networks have historically only needed to work. Working efficiently was never on the agenda. As long as occupants had hot water and heating that was job done. And with gas as a standard heat source, there was no need to be careful about temperature drops or commissioning valves to work as they should.

So now we are in an end of the world scenario and just waking up to how poor building services have been in reality. What we do next needs to work, and work well. We can't afford any more theories or excuse our delay on a lack of suitable technology. We have everything we need, technically, to deliver superb value for money low carbon heat networks, but as long as people follow opinions rather than data it will be impossible to effect real change.


Presentation to UKDEA

To view a full presentation about our Heat Network Optimisation services and various other topics, please watch the video below. You will find our Heat Network Optimisation presentation beginning at 1 hour in.


History

The past five years has seen a huge focus on HIUs. It was obvious that HIUs were one of the root causes of inefficiencies, with a wide variety of designs and levels of quality, and a strong tendency for the industry to value engineer out anything related to efficiency. Establishing standards was a very important first step, and the BESA independent testing gave us that. We were lucky enough to be in the first set of tests, and have been heavily involved since. Our hydraulics and controls expertise delivered us the best test results by far, with return temperatures not far off theoretical perfection, and have never been matched in the years since. This is not said as a boast, but rather as a testament to the use of data to develop products that actually work. Without a proper feedback loop, it is impossible to improve technology, just as it would be to improve a recipe you never taste.

Heat networks as a whole are no different. To the untrained eye energy centres generally look like impossibly complex. Looking at schematic drawings on the walls they appear to be highly engineered machines. But once you get to know them, its quite a different story. The layouts of most energy centres often makes it impossible to run a an efficient system, even once the network itself is delivering decent return temperatures. The use of headers and bypasses has historically been prolific, boiler sequencing rarely works, buffer stores are rarely used, and where they are used are never installed correctly. Pumps and boilers are commonly so oversized as to make it impossible to match low load conditions without rapid cycling, and usually end up running on some dodgy BMS logic to prevent them locking out.

As a backdrop the reader must understand that for more than a decade, official guidance has been inaccurate on the most critical matters such as pipe sizing and diversity methodology. To follow guidance has directly resulted in grossly inefficient networks, and the problem was only recently addressed by the CP1 pipework steering group. Pipes three times larger than they should be and nobody, anywhere seemed to notice or care. DS439, that steers UK sizing for many years, was only translated into English this year. And still, pipe sizing (velocity) guidance if out of date and in dire need of updating for modern pipe noise levels, materials, and instantaneous loads (that is said as an author of the current guidance ref. IOP Building Engineering Services Design Guide). We have a herd of Elephants in the room.

One of the best examples of how reality differs from practice is radiator balancing. A critical factor in achieving low return temperatures, yet in practice they rarely work. Only those network operators that have invested the time in monitoring know the truth of how difficult it is to achieve a 30C drop specified. In practice, anything more than 20C is doing very well in the UK. Yet there are simple well tested solutions used in other countries and on very rare occasion in the UK.

And then we come to the biggest hurdle of all, the controls. As manufacturers of HIUs and substations we often have a need to integrate with building energy management systems, however we have found this to be almost impossible due to a lack of centralised technical support to discuss modern protocols like MQTT. Almost all BMS systems are designed to lock one into contracts and licences rather than do the job at hand. Many BMS controllers are deliberately throttled down to enable them to charge for decent processor power (that you have already paid for). Every control point carries a licence, as does every modbus interface. You are then locked into a centralised network where problems like an IP clash can take down numerous sites at once. In short, it is simply impossible for anyone other than the employed BMS installer to write, check, debug, and improve controls logic. Its no wonder very few control panels have ever even been connected for remote monitoring, either because of the costs involved or for reasons of plausible deniability. Without any remote data, and nobody ever having the desire to even look, is it any wonder the things never worked?

Heatweb

At Heatweb we have been working for roughly ten years on the development of open-source monitoring as an in-house tool for product development. We are unique in the heating industry as pioneers of pre-fabricated thermal storage and plate heat exchange systems with many thousands of installed up and done the UK. Not just any standard system, but custom made, complex multi-fuel domestic heat networks of various sizes, all working perfectly. It is this experience that enabled us to achieve the unmatched HIU performances we have, and this experience comes from designing, building, deploying, and monitoring products in the field in order to improve them. We have been integrating heat pumps with boilers, biomass and solar thermal for decades, and nothing is guesswork or theoretical.

In our recent endeavours assisting local authorities with optimisation, we have learned that only open-source monitoring allows you to achieve success. It is the only way to beak the link between cost and efficiency - as long as it costs more money to add data points and functionality there is a point where commercially driven installers will stop. And where they stop is where you stay. As soon as data points and functionality becomes open-source and there is no additional cost to deploying an upgrade, then systems start to evolve. The ability to connect remotely into an energy centre and tweak the logic is not just a luxury - it is quite simply the only way the system can ever improve.

This is why nearly all optimisation contracts start with the installation (temporary or permanent) of a Heatweb control panel. Our panels are factory assembled and tested with the controls and communications we need to see what's going on, and then if needed take control of things. Components include a GSM modem, a touchscreen, power supplies, industrial I/O modules, an M-Bus master, Ethernet switch, and most importantly a set of controllers running open-source controls software. The software loaded into controllers evolves over time, and it is simple to copy and paste between systems, allowing added functionality, such as Modbus control of equipment, can be pulled in without any licences.

Such panels are very low cost, take a few hours to install, and provide a contract-free platform to access real-time data from the energy centre, starting with simple temperature and differential pressure data. This is in effect the same as when a Doctor initially may take ones temperature, blood pressure and heart beat when starting an examination. To do a proper examination you must be able to check the vitals. And check them properly - not every 15 minutes, but every second, continuously, day and night so we can see every little detail.

Once you start getting data, you start making informed decisions. Couple that data to a proper hydraulics expert and you get working solutions without any guesswork involved.

The greatest benefit of all with open technology is its easy to prove it works. There is a lot of data coming out of heat networks that have been successfully optimised to prove it beyond any doubt, including both HIU networks and those with centralised DHW storage.

Heatweb are asking local authorities to join in the open-source mission to improve heat networks.

Optimisation Package

  • Full examination of deign drawings (prior to site visits) to identify all potential problems
  • Examination of HIUs, risers, intake rooms, and energy centres
  • 6 month installation of Heatweb panel providing energy-centre communications, monitoring, and control abilities
  • 6 month installation of network sensors, providing DP and temperature data from strategic points
  • Temporary installation of HIU monitoring equipment into three properties
  • Data collection, dissemination and reporting
  • Detailed report on all problems identified and possible solutions
  • Updated schematic drawings of energy centre with corrected hydraulic layout and control arrangements
  • Optimisation of one property with before/after analysis
  • Cost benefit analysis on solutions

Following completion of the reporting contract, equipment can be removed or purchased.

The Heatweb panel provides the following functions:

  • GSM modem with 4G connectivity and fixed public IP address
  • Ethernet switch
  • Touchscreen interface
  • Inputs for sensors and equipment alarms
  • Outputs for valves, pumps and heat generators
  • Multiple Modbus interfaces for communication with equipment
  • Elvaco CMe3100 M-Bus master for meter connectivity
  • VPN secure remote connectivity
  • MQTT services

Heatweb Credentials

Why would a heat network operation choose Heatweb as their partner in optimising?

  • We have been designing and manufacturing equipment for heat networks since the 1980s.
  • We have many thousands of successful installations of domestic multi-fuel thermal storage systems across the UK
  • We have contributing authors to most heat network guidance from the original IOP guidance through to CP1
  • We sit on most technical steering groups, including SAP, MMSP, RHI, and CP1.
  • Our HIU (the DATA) has had the best VWART performance of any ever tested. We got near theoretical perfection 5 years ago and the rest of the industry is still playing catch-up.
  • We delivered the original heat network heat-loss calculation software
  • We have fully working schematic designs for all combinations of heat sources
  • We understand just about every valve and HIU that ever existed in detail
  • We have a vast list of case studies including:
    • Morden Hall: National Trust's flagship renewables centre
    • Queensland Road, Emirates Stadium: Custom designed storage interface units
    • Multiple local authority contracts over many decades
  • We have the biggest training centre in the UK
  • We have perfected open-source control and monitoring

Simple Solutions

There is no need for trial and error. We have been doing that for 30 years, reducing the error as we go, and we are now at a point where the same simple solutions can be applied to most networks to achieve both efficiency and zero carbon compatibility.

In our usual set of recommendations is a path to decentralise networks, moving from central gas boilers to distributed air source heat pumps. This is to enable upgrades to low carbon sources to progress from the property end of the networks, with existing plant online. This removes critical outages and allows smaller works to progress immediately.

  • Return temperature limiting valves on radiators, with network weather compensation.
  • Electronic HIUs for DHW, and direct heating where possible
  • Remove all bypass flow to obtain a true variable flow network
  • Open-protocol controls upgrade
  • Buffer stores used to sequence heat sources
  • CO2 Heat Pumps
  • Chrono-proportional room stats

We would strongly advice heat network operators to try the following without delay. These are low cost actions designed to collect facts and make informed decisions with your eyes open.

  • Test the performance of return limiting valves on a single property, with remote monitoring to confirm it works perfectly.
  • Look for locations where 30kW heat pumps (1-2 per 10 properties) can fit. Roof tops are the best location, and cranes are available to get them up there.
  • Fit remote monitoring at key points, temperature and pressure - network supply and index point. It will shine a bright light on BMS functions, bypasses and general health. Just a week is enough to see most sins.
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