Entrusted to Biomass

The National Trust, a charity dedicated to preserving the United Kingdom’s most priceless historic sites, is including biomass heat in its ambitious transition toward renewable energy.
By Tim Portz | September 18, 2015

Some form of Croft Castle has occupied its present day site in Herefordshire, England, since the 11th century. It served as a dwelling for the Croft family, as recorded in the Domesday Book, an early census method completed under the direction of William the Conqueror in 1086. Now, nearly a thousand years later, Croft Castle is being recorded in the first chapters of the story of the transition of many of the United Kingdom’s most treasured historic places to renewable energy. 

Croft Castle and over 300 other historic buildings similar in nature are owned, managed and cared for by a large charitable organization called the National Trust. Founded in 1895 as a reaction to the rapid pace of industrialization happening within the country, the National Trust was formed to preserve not only physical buildings, but wild places as well. The National Trust’s mission goes far beyond simply preserving its roster of castles and historic properties, as it also works to preserve the buildings’ contents, and whenever possible, make them available for the public to visit and enjoy. The task isn’t cheap, and it requires that the buildings have heat and power.

In July, the National Trust announced it was committing £30 million ($46 million) to an initiative that would replace fossil fuel energy inputs at its properties with renewable replacements, including biomass. The decision was made on the heels of a five-project pilot phase that included replacing a fuel oil boiler at Croft Castle with a biomass boiler.

Ed Wood, a renewable project manager at the National Trust, tells Biomass Magazine that this initiative began to take shape around four years ago when the National Trust really started to understand the potential benefits of moving away from fossil fuels and using local, sustainable sources. “Thinking about this led the trust to think more about renewable technologies,” Wood says.  Once it started considering renewables, Wood says the benefits and alignment with the National Trust’s mission just kept piling up. Chief among the benefits the National Trust immediately embraced was the long- term sustainability offered by renewables. “We hold many properties inalienably, which means that we can’t sell them,” he says. “So when you think about looking after these properties forever, being able to use a sustainable fuel source has got a massive advantage.”

 The board at the National Trust had its eye on the potential economic impact of a widespread transition to renewables as well. “Conservation work is hugely expensive,” says Wood.  “In 2014 and 2015 the conservation cost was £103 million.” In the case of Croft Castle, the grounds of the estate are more than capable of satisfying the fuel requirements that the new boiler requires. “The savings we generate we can put back into the conservation work,” Wood says.

As the National Trust is a charity and ultimately answers to its members, it is taking a stepwise approach to this renewable energy roll-out, and understandably so. Wood, remembering the organization’s direction, says, “The trustees had a look at what we were proposing, and they said, ‘If you do a number of trial projects and show us that you can appropriately install modern renewable technology in the buildings and the sites that we have, and over five initial projects prove that it works in all the ways you’ve talked about, then we’ll give you more resources to do more renewable projects on a bigger scale. “For Wood and the rest of the National Trust’s renewables team, this certainly raised the stakes of getting the system at Croft Castle right.

Challenging Deployment
While Croft Castle illustrates the benefits of a transition to a biomass solution, it also highlights the incredible challenges of installing new energy systems at historic sites. With a commitment to preservation being central to the National Trust’s mission, the urge to proceed with extreme caution with projects is understandable. “We really have to consider if everything we do in terms of installation is really justifiable,” Wood says. Still, climate control is a very necessary component of preserving buildings and the tapestries, carpets, furniture and artwork they contain. Without it, the varying temperatures and humidity would accelerate the deterioration the National Trust is working so hard prevent.

This caution extends well beyond the walls of the project buildings. “It also impacts the grounds,” Wood says. “In many instances, the grounds around a given building may very well have other archeological items in place. So again, we have to make sure we do everything by the book, and bring in archeologists to watch our digging and our trench work. And if we do find something, we have to change our route.”

With all of this in mind, the team at National Trust awarded the Croft Castle project to Euroheat, a leading biomass heating system installer in the United Kingdom. At the heart of the system Euroheat installed is an HDG Compact 200 wood chip boiler. The boiler is set up in a district heating configuration and delivers hot water to not only the castle, but also several different cottages on the estate, as well as the National Trust’s offices. The system is capable of meeting about 75 percent of the properties heating demand, replacing an older, inefficient boiler that typically consumed over 5,000 gallons of fuel oil a year.

The boiler will burn wood chips sourced from the woods immediately surrounding the castle. This contributes to the more active management of the surrounding woodlands and increases tree growth and overall biodiversity. Further highlighting how neatly the biomass boiler solution fits into Croft Castle, Wood notes that already in place there is a countryside team that looks after the woods on the estate. Early on, the project team decided that the grounds team already on site would be responsible for keeping the boiler fed with high dry, high-quality wood chips. “The grounds team brings in a contractor to fell trees, and they stack that wood in round form and dry it for up to 18 months before chipping it,” he adds.  Wood emphasizes that delivering chips to the boiler at the right moisture content is imperative to maximizing its efficiency.

In order to stockpile enough wood chips to maintain uninterrupted operation of the boiler throughout the heating season, a storage solution had to be devised. “We made a very appropriate wood clad, timber-framed structure for the wood chip store,” Wood says. Great attention was paid to not only the operational performance of this solution, but great care was taken to ensure that the new building blended in with the other buildings on the estate. “We had to keep roof levels very low,” says Wood. This challenging requirement paid off and yielded not only a solution that integrates visually with the site, but also offered some real gains in operational efficiency. “The byproduct of that is that we ended up with a sliding roof on the chip store,” Wood says. “We can slide the roof back, pour the wood chips in, and really maximize the use of the space without having a very big space.”

The installation was complete and brought online in September 2014. In its first season of use, the boiler consumed about 100 tons of wood chips. Finally, it is a true closed system, as the grounds team utilizes the ash for a soil amendment on the estate’s expansive gardens.

More to Come
The chip boiler deployment at Croft Castle is being viewed as a runaway success, and has put biomass heating in a good position to get a respectable share of the £30 million tranche of funds the National Trust has committed moving forward.

Wood and the renewables team are now moving on to the installation of two pellet boilers at a property in Warwickshire called Upton House. The grounds at Upton House are more compact than the grounds at Croft Castle, and make the deployment of a large boiler house and chip store impossible. As a result, the design team opted to deploy two pellet boilers supplied by ETA, each capable of producing 95 kW of heat. Two separate interior pellet bins will supply the boilers, which will heat Upton House, a restaurant, a cottage and an art gallery.

The Upton system will be installed by Purple Energy and  will consume approximately 75 tons of pellets each year and produce nearly 215,000 kWh of heat annually, satisfying nearly 50 percent of the site’s total energy needs. The site was not without its own challenges, however. It was not built with automobiles in mind, to say nothing of larger pellet trucks, and Wood’s team had to overcome a pellet resupply challenge before the project could be given the green light. “Luckily, we found a supplier with a smaller pellet delivery vehicle that can get down our driveway,” says Wood.

Other projects are beginning to work their way into the biomass heating industry within the United Kingdom. Neil Harrison of re:heat reports that his team successfully responded to a tender, or request for a proposal, for a project in North Yorkshire called Nunnington Hall. “In our years in the industry, we’ve never completed a tender quite like this one,” Harrison says. “These guys are very serious in terms of how they view their property portfolio.”

The system Harrison’s team designed has been configured to deliver lower temperatures at a constant rate. “This system has been designed to deliver mainly conservation heat,” he says. “The system needs to provide enough heat, year-round, to preserve the fabric of the building and the contents of the building.”

Not having to deliver enough heat to keep the building warm enough for continuous habitation allowed Harrison’s team to ratchet down their design. “Even for a massive place like this, we’re only putting in about 100 kW of pellet boiler capacity,” he says. “You would expect something much bigger.”

Through this experience, re:heat learned what every contractor working on a National Trust property must understand: Appearance and conservation are key. “Anything that alters the look of the building degrades it from a historical perspective,” Harrison says. “We couldn’t just stick a shipping container with a pellet boiler outside the building. So we needed to make very sensitive modifications inside the building to achieve the proper design.”

With the success at Croft Castle and the other pilot projects, Wood and the renewables team earned a license from the National Trust’s trustees to do more—£30 million more. The share of that tranche that biomass will earn is yet to be determined, as projects are still working their way through a robust evaluation phase. These first monies can’t possibly cover the needs of all the properties owned by the National Trust, but they can certainly serve as a broad proof of concept that renewables can meet energy needs, even in sites being actively preserved for their historical value. Moreover, with each successful project, the initiative cements its place in the National Trust’s long-term vision. Providing good sustainable energy is also vital to looking after these properties forever,” Wood adds. “There is a kind a tradeoff to be had in trying to install these technologies for the benefit of the property while doing  it in a way that is really sympathetic to the history of the site—it’s  good fun.”

Author: Tim Portz
Executive Editor, Biomass Magazine
[email protected]