This short article is an invitation to the ground source heat pump community to engage with brown field practitioners involved in remediation of soil or groundwater to enhance the ef ciency of both energy exchange and remediation. Brown field sites have been affected by former uses of the site or surrounding land; are derelict or underused; are mainly in fully or partly developed urban areas; may have real or perceived contamination problems; and require intervention to bring them back to bene cial use (CABERNET 2006; World Bank 2010).
Far from all brownfields are contaminated. However those that are contaminated and require remediation to ensure they are suitable for their intended use offer opportunities for ground source heat pump that can increase the economic attractiveness of GSHP solutions and contribute significantly to a positive evaluation of the sustainability of the overall reclamation. Process based remediation technologies (Nathanail et al. 2007) can create opportunities for GSHP to re-energise brownfield sites and greatly enhance the cost effectiveness of such solutions but only if remediation and re-energising are considered in a timely and integrated manner.
Table 1 Reusing brownfields – a stepwise approach
| Activity | Comment |
| Redefining the site | Brownfield sites are essential components in dynamic urban land management. Changing land uses allow urban systems to develop and avoid stagnation. |
| Remediating unacceptable risks | Those brownfields that are contaminated require chemical, physical, biological or conventional engineering intervention to ensure they are suitable for their next use. |
| Reclaiming land | Brownfield often contain remnants of former land uses that need to be removed prior to the land being reused. Such remnants can include foundations, utilities, traffic infrastructure, unsuitable materials. |
| Re-energising the site | Brownfield have traditionally made use of conventional grid based energy supply or on site generation sources. Current attention on renewable energy sources gives brownfields advantages over previously undeveloped land, |
Groundwater in urban areas is often polluted with volatile organic compounds such as hydrocarbons and chlorinated solvents. The way in which such groundwater is remediated may also allow energy exchange processes to take place. Pump-and-treat involves pumping groundwater out of the ground, treating it and then reinjecting the clean water back into the ground. Since the energy used to pump the groundwater is accounted for against the remediation process, it is ‘free’ to any energy exchange process that could exploit the energy storage capacity of the water. On a large scale this being carried out in the Netherlands where water is pumped to protect areas from inundation. On smaller scale industrial sites, pump and treat is seen as an expensive long term – quasi permanent – means of containing groundwater pollution. Existing pump and treat schemes may offer low cost quick win opportunities to demonstrate the benefits of GSHP on industrial sites.
Permeable reactive barriers (PRB) were developed in the 1990s as an alternative to pump and treat. Instead of pumping the groundwater out of the ground, a treatment zone is placed into the ground to intercept natural groundwater flow. Polluted groundwater flows through the treatment zone and emerges clean down gradient of the PRB. The residence time within the PRB is an important design consideration. Heat exchange infra structure can be installed immediately adjacent and downstream of the PRB at little extra cost – the bulk of the permitting and excavation expense is charged to the remediation works.
Contaminated soils are sometimes treated in situ or capped but most often are excavated for treatment or off site disposal. Where excavation is involved, the resulting void is usually backfilled with imported inert material to make up the site levels. However the expensively created void could be seen as an asset. In a GSHP context, the void could allow the installation of shallow GSHP infrastructure with the cost of excavation charged to the remediation.
The above discussion has shown how costs charged against remediation can be piggy-backed by GSHP solutions to enhance the overall sustainability of brownfield reuse and make GSHP more economically viable.
The CABERNET ABC model (CABERNET 2006) has been adopted by national regeneration agencies such as English Partnerships (now the Homes and Communities Agency) and international funds such as the European Bank of Regional Development JESSICA fund. A-sites are those whose reclamation costs are more than outweighed by the final land value and are therefore commercial viable. C-sites are those which are not economically viable as reclamation costs preclude profit. B-sites are marginally non viable and are usually seen as those sites where the public sector can create the conditions for the private sector to step in and complete the redevelopment process.
An integrated approach to remediation, reclamation and re-energising (Table 1) can change the economics of sites and push B-sites into A-sites and C-sites into B- or even A-sites. However this requires early consideration of the integrated land reuse strategy and a broader outlook than traditional linear, sequential thinking. Such ‘smart’ thinking can be a major contributor to both successful reuse of brownfields and greater take up of GSHP technologies.
References
CABERNET (2006) Sustainable Brownfield regeneration. Millar K, Grimski D, Ferber U, Nathanail CP. (eds). Land Quality Press: Nottingham. http://www.cabernet.org.uk/resourcefs/427.pdf. Accessed 14 November 2011.
Nathanail, C.P. 2011. Chapter 25: Sustainable Brownfield Regeneration. In: F.A. Swartjes (ed.), Dealing with Contaminated Sites, Springer. pp 1079-1104
Nathanail, J.F., Bardos, P. and Nathanail, C.P. 2007. Contaminated Land Management Ready Reference, EPP & Land Quality Press: Nottingham, 2nd edition.
World Bank. 2010. The management of brownfields redevelopment: A guidance note. World Bank Europe and Central Asia Region Sustainable Development Department.
