Local Authorities and Housing Associations
What's changed ?
Recent advances in our understanding of how heat networks function has now shed a clear light on the reasons why historically they have performed so badly.
There have been very few records kept of how heat networks have performed over the years, and the difference between design efficiencies and delivered efficiencies is written off as almost a mystery. Poor installations are a common problem, as well as windows being left open, letting the heat out. Where heat meter data has been analysed on existing networks and compared to heat generation, efficiency figures as low as 50% are no surprise, with some networks as poor as 25% efficient.
Now, with the data from recent tests funded by DECC, we know why, and how to solve it. We have independent test data on most of the common HIU manufacturers, and we have calculation tools to work out the heat losses from pipework relative to energy used on hot water and central heating based on the test data.
The reality is the design and operation of systems has been as much, if not more, of an issue than installation, and occupants often need to keep windows open to get rid of the excessive quantities of heat pumped into buildings by inefficient networks. A cool hallway or HIU cupboard would normally be seen as a fault - when actually it should be normal. Even the recent SAP proposals for heat networks detail efficiencies as low as 30%. That's £2.30 wasted for every £1 used. If district heating were a regulated industry, a lot of systems would have a lot to answer for.
Using test data and calculation tools we can establish exactly where the 50% (or more) losses go, and more importantly they demonstrate the means to increase efficiency levels up to 85%.
Who are you going to believe ?
Certainly, you shouldn't only be taking the word of a manufacturer such as ourselves. It is in our interest to have you believe our products are the best on the market. Once you get to know us you will discover we always give unbiased advice and our products and service levels really are quite revolutionary.
But until then, we would instead refer you to the independent tests carried out at the Swedish Institute of Technology. They were funded by DECC to ascertain how HIUs actually perform, and to provide hard test data in real life operating conditions that can then be used to work out real world efficiency. The tests were taken from the existing Swedish standard and modified to suit UK operating conditions, and it was agreed by all manufacturers taking part for the results to be made public. The standard can therefore be used as part of a specification.
The following graph shows the results of recent tests, on many of the biggest makes of HIU. The height of the bars represents average annual network return temperatures (by volume), the width represents annual volumes used, and the area represents the volume of energy returning to the plant-room.
The difference in size between the bar on the left, a typical HIU in London, and the bar on the right, the best modern HIU, is startling. Some people have jumped to the conclusion that the tests have been manipulated, or performance has been sacrificed. However the independent tests cover performance, and show that the modern HIU not only improved efficiency dramatically, it also had the highest performance of any HIU tested, reaching full tap temperatures in the fastest time, and delivering higher outputs. They are also carried out at one of the most respected test houses in Europe, the Swedish Institute of Technology, to a rigorous test procedure.
Making use of this test data we can now calculate efficiencies of networks using online tools, providing detailed and thorough operational heat loss figures throughout the year, to arrive at seasonal efficiencies.
So now that we have independent testing and heat network efficiency is no longer a mystery, ensuring your heat networks are capable of running efficiently becomes a matter of running the calculations, and then specifying an HIU that has undergone testing and achieved the necessary performance level.
Links to Information
Heat Network Calculations
- Worst case heat network... (pre 2010)
- Best case heat network... {2016)
Why isn't this common knowledge ?
The HIU test results are new, and a first in this industry. Up to now consultants have only had a manufacturer's word to go on regarding performance, and there have been no tests to hold manufacturer's accountable.
The test results are damning for most of the industry. Many would like to see them brushed under a carpet. To see such standards built into regulations would spell the end for most products on the market.
The industries record on monitoring the performance of existing networks is atrocious. Even with heat meters fitted on sites feeding back detailed information on flow and return temperatures, enough to diagnose there is a big problem, the data has gone unread.
Will this solve all the problems ?
Even with the most efficient HIU in the world, we would still argue that you are not safe. There is still a lot that can go wrong on the ground, for example:
- Dirt and blockages in pipework
- Flushing bypasses left open
- Inadequate flow around network due to poor pump control
- Wrongly commissioned HIUs
- Lack of balancing on radiators
- Leaks in pipework
- Lack of dosing
- Missing insulation
- Tampering
It may be a surprise to learn that every single one of these problems can also be solved using the latest HIU technology.
In short, HIUs send out a wealth of sensor data, calculated parameters relating to network performance, and alarms when things are not perfect. These can be channeled through a network - the same network used for billing and metering - and used to confirm 100% performance, without setting foot on site. Indeed, the whole process can be automated so one receives an email the second something goes wrong.
Where you have historically relied on the competence and honesty of consultants, manufacturers and installers, you can instead confirm for yourself how everything is working by simply referring to a browser based dashboard with live performance information.
This is the kind of technology you may expect to see managing a plantroom using modern BMS systems, however applied over the entire network.
Revisiting our list of problems we can now offer some specific solutions...
- Dirt and blockages in pipework - differential pressure readings from the HIU can be compared to the design pressure drops. If the pressure drops are too high it means there is a blockage and an alarm can be raised.
- Flushing bypasses left open - again, differential pressure readings give an indication, while it is also measurable by comparing flow rates from plant to the sum of flow rates from HIUs. Again, alarms can be raised.
- Inadequate flow around network due to poor pump control - once again, differential pressure measurement is the key. Linking the signals from the furthest HIUs to pump control will ensure proper function.
- Wrongly commissioned HIUs - the HIUs tell us what they are set to, and can be altered remotely. In fact, when a new HIU is plugged in, the system sets it up automatically.
- Lack of balancing on radiators resulting in elevated return temperatures - the HIU limits return temperatures to protect the network, and return temperature readings can be used to flag an alarm that a system is poorly balanced.
- Leaks in pipework - pressure sensor readings in the central heating circuits tell us if pressures are dropping.
- Lack of dosing - achieved by linking in pH sensing.
- Missing insulation - with flow temperatures monitored second by second, a 3m length of missing insulation results in a visible dip in flow temperature readings, and can be spotted remotely.
- Tampering - the moment a sensor is unplugged, an alarm is logged and raised.
Costs and Risks
Are Modern HIU Systems Costly ?
The short answer is no.
Modern electronic HIUs are no more expensive than good quality mechanical HIUs. That said, you will always be able to find something cheaper. It is indeed one of the reasons we see independent testing as so important. Without it a manufacturer can always sacrifice efficient operation for cost, and deliver something cheap that delivers target hot water and heat outputs. These are the tactics used to value engineer, or break specifications by offering a saving. The problem is if you take into account the effect on running costs, something manufacturers and installers care little for usually, then the savings evaporate and one is left with a legacy of a heat network that potentially costs double to run than it should.
What about the cost of the hardware for monitoring ?
Again, the modern world has come up with a solution - open source Linux systems. Many will have heard of the Raspberry Pi. A £25 computer used in education with built in WiFi, Ethernet, Bluetooth (old and new), USB Ports, and HDMI desktop output. Well it can also be used to send data or alarms from heat meters and modern HIUs. They can also provide Mbus and Modbus connectivity, and as such offer a low cost means to bridge HIUs to other systems, monitor and control them.
With many billing platforms making use of the same software languages, the software functions developed on a Linux system, such as a Raspberry Pi or Arduino Yun, can be implemented on them also. This means that no additional hardware needs to be used at all to connect to HIUs.
Is there not a risk of being locked into a bespoke system ?
Certainly not.
We have based our communications technology on standard protocols that can be replicated on other systems, and the benefits of an intelligent HIU come as standard - you just need to make use of them.
We also assist in the connection of HIUs to 3rd party systems. As an example, to assist in the delivery of Ofgem's MMSP - Monitoring and Metering Service Package - we worked with the Energy Saving Trust to develop and publish Python code to send data from heat meters and HIUs to the Trust's EMBED database, and thereby enable contract-free monitoring of RHI installations using low cost electronics.
Carbon Costs
With the new requirements for zero carbon domestic hot water in London, one needs to also consider the costs of offsetting carbon.
Given there is potential in many instances to save 50% of the energy required to deliver DHW over a heat network, by using the right controls strategy, that's one huge step towards achieving zero carbon. It makes the percentage of any zero carbon generated on site twice as effective, with less carbon to offset.
It will also impact on CHP sizing. As CHP is sized to deliver the baseline load, so they run continuously all year, we are talking about the DHW loads as well as the heat lost from keeping the network hot at all times for DHW response. With 50% or more of this load gone, the CHP sizing should drop accordingly.
With average annual return temperatures from a heat network below 25°C now possible, the percentage of waste heat that can be used on a network increases significantly, as does the effectiveness of technologies such as heat pumps. Return temperatures this low enable a proper bivalent system to be used, with heat pumps raising temperatures from 25°C to 50°C, and gas boilers or CHP raising it further, typically to over 60°C in the Summer and to 75°C in the Winter. There goes another chunk of carbon and the costs associated with it.
Additional Benefits
Being able to manage how HIUs perform automatically opens up some exiting possibilities.
Traditionally systems are sized and set to meet peak DHW load, on top of central heating when it's -5°C outside. The thing is its rare to see peak DHW load, and when you do its a brief spike. Furthermore, its even rarer to see -5°C outside, however the standard HIUs being fitted forbid you from dropping the temperature of a heat network to save energy. With responsive HIUs that can automatically react to a lower network temperature, it finally becomes possible to run the network temperatures depending on load, without adverse effects.
Next, if you look at the peak loading of a system, hot water load and central heating may each account for roughly half of the flow used by the heat network.
What then, if at the rare times loads spike and get close to peak load, the system could simply turn off the central heating load across the site for a few minutes ? Your pipes only need to be half the size ! Looking at it another way, where a heat network has been sized using traditional load profiles, it may well be possible to double the number of properties connected. By managing the load intelligently using modern HIUs.
A few final bonus features we can offer...
- Pre-pay shut-off features built-in without the need to fit additional valves.
- Frost protection on unoccupied properties, or those on pre-pay shut-off.
- No loss of pre-paid credit caused by heat loss from an HIU.
- Concierge dashboards for health care properties.
- Legionella safe operation.
- The best district heating installer and specifier training in the UK.
- Thermal storage and hot water storage options.
- On-site manufacturer support.
What next ?
Visit our one day exhibition at the Building Centre, in Store Street, London, on 17th January 2017, aimed specifically at local authorities in London trying to achieve zero carbon domestic hot water.
{{#l:InviteJanuary2017.pdf|Information on Building Centre Event}}
- View our case study with Network Homes... Press Release
- Have a play with the online Heat Network Calculator. It will allow you to quickly checkout the efficiency calculations on a riser system and see the effect of changes. This is a thorough tool that takes data from independent tests. Some examples...
- Check out the information on the industries officially most efficient HIU... The DATA HIU
- Learn more about the technology... The HIU Revolution
- Check out the information on our latest low cost monitoring platform... Data Monitor v1
- Have a look at some of our historic contracts to be sure you are dealing with the best there is.
- We would like to demonstrate the technologies discussed. We happen to have the UK largest renewables training facilities, covering everything from wood burners to district heating. Therefore we would prefer to do a demonstration at our place, where all the technology is on working display, but will happily bring an HIU to your offices and give an approved CPD and work through some calculations with you.
- Book in your district heating design team for the latest training...
- We would offer to assist in the installation of a few monitoring devices. This is to give you a flavour for how well your existing networks perform.
- Give it a go. Allow us to assist you in setting up a small number of properties using the technology we have outlined. Other local authorities and housing associations are already reaping the rewards. Please see our Offer to Local Authorities.
