The HIU Revolution
This article has been inspired by the recent publication of independent test data on a spread of Hydraulic Interface Units, as well as by the ensuing technical discussions.
To us it is fairly clear how a modern heat network should run, and the fact that we "spanked" the test proves we have an idea or two up our sleeves.
This article explains why its time to throw out the existing book, and embrace the revolution.
Accuracy of Data
The data used in this article is extracted from the published test data from recent tests carried out at SP in Sweden under the new UK testing standards.
Key Advances in Technology
At the core of the revolution is the shift from mechanical systems to electronic. Believe it or not, the district heating industry still clings to the concept that mechanical is best and more reliable. This is simply down to having not yet experience an electronic system from a reliable manufacturer. No surprise then that systems costing upwards of a million pounds, and responsible for delivering our most important and costly services, are generally still less intelligent than a wristwatch.
There is however no doubt that the ability of electronic systems to deploy advanced control strategies, using just the one valve per circuit, enables systems to become more advanced without the need to add more and more valves (or valve components).
The introduction of electronics also enables networked communications. It allows remote management of settings, remote fault alarming, and holistic heat network functionality.
The nice thing is, there is usually all the hardware already in place to allow this networking to take place, in the form of a billing system, and we will in part cover the latest advances in this arena.
The real breakthrough that has been made in the HIUs, enabled by the use of electronics, is the way the systems manage the volumes and times that primary heat is drawn, in order to manage the heat network in its entirety. The effects on heat loss and volumes circulated is, as the independent data proves, quite revolutionary.
Efficiency of District Heating
We believe this can be split into four categories:
- Generation efficiency - how efficient the plant room is at generating heat, and typically a function of return temperatures.
- Heat losses from main network flow pipework - this is the distribution pipes that carry heat to homes and need to be maintained at temperature.
- Heat losses from branch flow pipework - these are the pipes in the vicinity of properties, that can drop in temperature (conditions apply) without affecting performance.
- Heat loss from return pipework - this includes both branch and main network pipes and reflects the losses of heat from unused heat returning to plant.
