Are Ambient Loop Heating Systems the future?
Energy targets on new developments continue to push us towards a zero-carbon standard. That, combined with the Government’s plan to phase out fossil fuel heating in new builds, means designers are coming up with innovative heating ideas.
If you’re working on a large site in London, you’re expected to install a communal heat network – especially if you’re in an area where District Heat Networks already (or will shortly) operate.
Communal heating has plenty of advantages in a city environment. The large scale operation means they are more efficient… it’s easier to retrofit one large system than 500 individual boilers… and in the future, when we’ve invented a yet-unknown zero carbon heating solution, the city will be able to switch over thousands of homes in one fell swoop.
But there are drawbacks – one key issue is the operating temperature. DHNs need a hotter flow, which brings an increase of heat loss from pipework. Estimates on current systems suggest 20-50% of the heat generated is lost before it reaches the dwelling.
As well as producing high levels of waste, this lost heat often spills into communal areas, causing overheating.
If the flow temperature could be lower, losses would be lower, which would reduce overheating risks, and would also reduce fuel bills for occupants (who wouldn’t be paying for all that wasted energy).
This brings us onto Ambient Loop heating systems. This is a two-stage heating design which tackles the issue of distribution loss. You still have a plant room, but it operates at a much lower temperature (15-30 degrees instead of 60-90). The lower flow rate means less distribution loss (less than 5%) between the plant and the dwelling. A small heat pump sits in each flat which tops the heat up to a usable temperature.
Ambient Loops can include cooling also, as it’s possible to remove excess heat from one dwelling and send this energy back into the loop to provide heat or hot water elsewhere. This has the added benefit that conventional roof chillers aren’t necessary.
But even this isn’t a perfect system, and it comes with its own drawbacks.
One big concern is how to define it. Can / Should a communal heat network have individual heat pumps in every dwelling? This makes things complicated when parts need replacing.
Secondly, the extra machinery required means the embodied energy of the heating system is higher. The GLA want to introduce Whole Life Carbon assessments on London’s largest new developments. WLC measures the carbon footprint of building materials from creation to demolition. The more components in a development, the worse WLC rating a building will achieve.
Thirdly, Ambient Loop systems aren’t particularly compatible with conventional networks. If the Ambient Loop operates at 20 degrees, it isn’t going to be happy being connected to a neighbouring network running at 80.
The GLA recently announced in their April 2020 Energy Assessment Guidance that it will not support schemes that plan to use ambient loop systems if they are in an area where existing District Heat Networks are a viable option. We are waiting on further clarification on their reasons for dismissing this technology, but we expect those outlined above will feature heavily in their answer.
So, if city sites are still being encouraged to use District Heat Networks, but Ambient Loop systems aren’t in the equation, and fossil fuel plants are getting the cold shoulder, what’s the solution?
There is no silver bullet for this question. Heat pumps are certainly going to become more common on new sites in the short term as we see CHP systems fade away. Longer term a hydrogen gas alternative could challenge heat pumps for being the greener option. But whichever prediction you look at, your traditional community heating setup has most definitely been assigned to the history books.