A centralized boiler system, servicing consumers via a district heating schemes (DHS, also known as heat-networks), is not a new idea. They are used extensively in China, Russia/ former CIS, East Europe and elsewhere – largely for heating commercial and residential blocks. DHS is also used in the UK, although the trend has been to move away, largely because of high maintenance costs, distribution losses and the fact it is difficult (and costly) to sub-meter therefore apportion costs fairly.
Recently, Local and National Governments have been exploring ways to handle wastes, particularly municipal solid waste (MSW), other than landfill. Turning this waste into energy is one option – albeit lower on the waste-hierarchy than recycling.
There are many examples in the UK of schemes that convert waste into electricity. Why electricity? Well, it is relatively easy to feed into the National Grid, one is guaranteed a decent export price plus the added benefits of attracting renewable obligation certificates (ROCs) or Feed-in-Tariff (FiTs) and local electricity certificates (LECs).
But can one get more from this “waste” energy? Clearly, one generates a lot of heat from burning the waste, but there are only a few examples of heat-sales. Why? Partly because, until recently, Energy from Waste (EfW) heat sales only attracted the value of the heat, giving it little hope of competing commercially against electricity. Furthermore, heat is not very transferrable; realistically it can only serve local consumers. Distribution costs are expensive, particularly the up-front costs (and disruption) from building the heat network, which need to be recouped. This necessitates a need for long-term supply contracts, to which many organisations are reluctant to commit. Finally, whereas electricity demand is high all the year, heat needs vary considerably between winter and summer; therefore to make any DHS attractive one needs to plug into consumers with high, year-round heat-needs.
But the situation is dynamic. The UK Government has set itself a target of 12% of heat to come from renewable energy (RE) sources by 2020, looking to offset 44 Mt CO2/y. DECC’s recent announcement on the renewable heat incentive (RHI) is designed to help encourage the generation and export of RE or part-RE heat to local consumers.
For this, “heat-mapping” the area around to the proposed EfW site is strongly recommended. To date, Paul has carried out 5 such “heat-mapping” exercises in different parts of the UK. For each, there was good potential for heat-sales, but the up-front costs and risks associated with DHS, combined with the uncertainty of the RHI tariffs, generally made power-only generation from the waste the default position. Now that DECC has announced the RHI tariffs, it is believed that the potential for EfW heat-sales to local consumers can and will take on renewed interest.
Industrial “reject” heat
During 2013, Paul participated in a DECC funded “Industrial Reject Heat” study. Its aim was to better understand the quantity and characteristics of heat rejected from energy-intense industrial process, and to explore ways of recovering more of this heat. The work necessitated visits to a cross-section of organisations representing major energy-intense industrial sectors, plus discussions with site representatives and Sector Associations.
Most energy intense organisations, particularly high-temperature operators, already recover heat and use it to pre-heat the air/ incoming material, or for lower-temperature processes elsewhere on site. Often these heat-recovery units are built into the process: regenerators, recuperative burners, to pre-drying wet-formed product, pre-calcining raw material, etc. For many, the only time they can upgrade further is during scheduled re-builds.
However, few have considered the option of exporting to neighbouring sites – either direct “across the fence” or via a DHS. As with the EFW schemes, the high up-front costs, variable seasonal demand plus other commercial risks, not least long-term contract lock-ins, make it unattractive. Also, heat-sales are not their core-business, so is outside their comfort zone.
Again, the situation is dynamic. If Government is keen to meet its commitments to low-carbon heat generation, one potentially cost-effective route would be to incentivise ways to encourage greater tap-into this “brown heat” (parallels with “green-field” and “brown-field” developments). Heat mapping of local area(s) for potential consumers, combined with understanding their drivers and risks, would be an important early step in this process.