One problem, three engineers, no constraints
“How can we get the benefits of district energy, where a central heating or cooling plant serves a number of buildings, without the huge upfront investment in the system? We often proceed with our projects on a building-by-building basis, and each building alone can’t sustain the capital investment to build the central plant or main heating facility. Historically, in Europe and particularly in Scandinavia, the investment tends to be made by a public utility. In the absence of a progressive utility that is prepared to do that or has already done it, what low-hanging-fruit solutions could we apply?”
John Filipetti / vice president, design and innovation / Oxford Properties
Make sure you are future-ready
Bruce Geldard / technical director, energy services / WSP / UK
If you think about the benefits of district heating, it’s lower cost, lower carbon and gets rid of the risk and responsibility of running your own equipment. By designing your building to work with modern energy recovery systems and switching to an arrangement where your energy company provides heat to you as a service, you could harness these and build up from a relatively small level. The starting point is to think about it from your building out. When a district energy scheme does come along it will likely be designed for relatively low temperatures, so you need to find ways of keeping occupants comfortable without high temperatures circulating around the building. That means underfloor heating, chilled beams, maybe air systems to help make the building as efficient as it can be.In future, this could mean integrating phase change materials to turn it into a store and a smart user of energy. These will cut costs and energy while also making you as ready as possible to connect to a future scheme.
You also need to be ready to share energy both inside and outside the building, applying the “prosumer” idea of being both a producer and consumer in one. By integrating photovoltaics for electricity and thermal, for example you can harvest renewable energy and hopefully send the excess off elsewhere. If you’re not connected to a network, you can look at how to store it onsite.
Many district schemes are looking at running as a shared loop, or fifth generation network, enabling people to harvest waste heat from, say, a data centre a couple of blocks away. The key integration here is a water source heat pump, which adjusts the temperature on the network to what you actually want. Your building must be ready to take a water source, and you either put in the heat pump, or allow for temporary provision of one type of system and switch over later. There are also trials for loops that effectively take energy from one building and share it with another. The fundamental principle is to use every ounce of energy we’ve got, whether that’s by sharing it within a building, between neighbours or across a whole city.
“Where the energy comes from could be quite outlandish … I’ve seen pictures of people walking on treadmills at their desk”
Where this energy comes from could be quite outlandish. Maybe you’re providing wellbeing to your staff by letting them exercise while working and as a result they’re putting energy back in. I’ve seen pictures of people walking on treadmills at their desk — but that’s a bit Matrixy! More simply, if you have something that produces excess energy, or needs more, there’s probably a value in that to someone else. Every commercial building has a server room that needs to be kept cool, while someone in the next building is feeling cold.
The other aspect is the contract with your supplier. Lots of energy companies are looking at providing heat as a service, so effectively contracting for comfort. This gives more certainty on cost and is more intuitive: no one wants to buy kilowatt hours we want to be warm or cool. And you want experts running the equipment rather than it being a sideline you have to do just to keep your building operating.
Connect to smaller centres, and use all available heat
Anna Boss / systems researcher / WSP / Sweden
Kerstin Wangsten / project planner / WSP / Sweden
This is fundamentally about planning and collaboration. The traditional approach to district heating is to build an enormous expensive plant or boiler and connect buildings to it. But we want to move in the direction of having several, smaller heat production centres, using locally available heat and fuel. If you begin with a masterplan of the city or district where you want the system to be, you can see what heating and cooling demands are in an area and what possible supply there is — perhaps industries with excess heat, like a paper mill or steel plant, or even a sewage works.
This wouldn’t replace centralized heat production entirely because you need a reliable supply, but it could mean smaller plants than traditionally used. Starting small is good because it means you don’t need big upfront investment. And small-scale networks can be connected later. You can also start with the buildings in an area that are most profitable, further strengthening the investment case.
“When different actors talk to each other, it’s easy to find efficiencies”
Collaboration can also slash construction costs. In areas with new buildings that need heating, electricity, water and sewage, it seems obvious to dig for all these services at the same time. But it’s not always done that way. When different actors talk to each other, it’s easy to find efficiencies. It’s the same for existing areas with ageing piping too. It makes sense to put down new pipes at the same time as you are changing the water distribution system, for example.
A single player can’t do this alone. Municipalities need to be involved for the level of collaboration needed. But it’s also about making the opportunities for different sectors visible — for example, showing private industries how they can earn money by selling their waste heat instead of using cooling towers.
Getting agreements is complicated, but we’re certain it could be profitable in many more cases than are currently being developed.
Go big — and avoid the “red zone”
Bill McLean / director, thermal energy / WSP / Canada
Adam Patterson / senior engineer, structures / WSP / Canada
There’s no way to avoid a huge capital outlay. In fact, the goal is to make it as large as possible, to minimize the cost per unit. If you build a plant to heat one building and it costs $1m, a plant to heat ten buildings probably costs less than $10m, and a plant to heat 20 buildings is far less than $20m. If you expand your philosophy to include not just heat but electricity with a combined heat and power plant, the cost per unit is even lower. It’s the same with waste heat recovery — the more buildings you have, the more energy you can recover from waste heat sources. That will help to reduce the size of the plant and the initial investment. If there’s a large hospital or correctional facility nearby, or something else very large, that could be a base customer, so you know there’s already a significant demand that will provide a revenue stream.
“Alternatives to burying pipe? You could make it a piece of public art …”
If you’re building a district energy system from scratch in a downtown core, the costs are very high because you have so many constraints. Ideally, you need a whole bunch of buildings next to each other with some flexibility. Then you can find out if there is critical mass in terms of demand, and what the existing plant looks like in each one. One of them might house the central plant, which could mean repurposing a portion of a buried car park or the existing mechanical rooms. If you’re building a new tower — and you have a very large hole in the ground — you could capitalize on that to connect to buildings immediately adjacent.
There are some really clever technical solutions and innovative drilling techniques. There are also alternatives to burying pipe. For a new district energy system in Arlington, Virginia, we ran two 12indiameter pipes all above ground, to save the cost of burying them 4-6ft underground and ripping up half of the downtown core to do it. You could make it a piece of public art, or just the interconnection between buildings.
Or you can go extremely deep with directional drilling or a micro tunnel-boring machine. Whatever you do, don’t go in the “red zone” where all of your existing utilities are. As soon as you have to dig anything up, it adds a huge amount of time and coordination, so shallower solutions that seem cheaper are actually monumentally more expensive.