By Steven Kenway*
Energy costs for water utilities are large, and growing
Energy is a significant cost for many water utilities, and costs are growing as more energy-intensive forms of water supply, including desalination, are being used. Energy is typically the second-largest utility budget item in developed countries, after labour. In many developing countries, energy can account for 70 percent or even more, of annual costs. But water and wastewater utilities can generate and export energy–in multiple forms.
Water utilities can generate significant flows of energy
There are many examples of water and wastewater utilities successfully implementing Distributed Energy Resources (DER) projects, to offset costs, improve reliability or meet other targets such as greenhouse gas emissions reduction. Biogas (digester gas), co-digestion of food waste, heat generation (incineration of sludges), wind- and hydro- turbines, solar photovoltaic, tidal and geothermal, algal systems and fuel cells are all practical examples that have been proven to work.
However, current generation of renewable energy by water and wastewater utilities is a fraction of its long-term potential. In the United States, municipal water supply consumed 40 billion kWh electricity, and wastewater treatment 30 billion kWh in 2012: collectively 2 percent of total national electricity use. Yet the thermal, chemical and hydraulic energy content of raw wastewater alone in the United States is ~150 billion kWh, with 80 percent of this as waste heat, and 20 percent as chemical energy.
Globally, a number of wastewater treatment plants, including Morgental in Switzerland, are capitalising on all these forms of energy, and expect to generate more than five times than the plant itself consumes.
Water utilities are well placed to connect to electricity, gas and heat grids
Water and wastewater utilities are often good candidates for Distributed Energy Generation, and integration with electricity, gas and heat grids. They often own large amounts of contiguous land, have high (and movable) energy demand, and have the ability to provide other services to the energy grid. However, this integration is slow. Of the approximately 837 biogas generating facilities in the US in 2013, only 35 percent generate electricity from the gas and only 9 percent sell electricity back to the grid.
Integrating with–not just connecting to–the electricity grid is key
Successful integration of DER systems into the electric power grid can be problematic when the grid is not designed to accommodate high penetration of DER. To realise fully the value of DER and to serve consumers reliably, integrated planning–and an Integrated Grid–is needed.
Lack of co-ordination, is creating a wide set of barriers to integration and a raft of additional challenges exist including policy instability, guarantees, reliability, and maintenance responsibility. Identifying best options, and navigating regulatory requirements, tariffs and other barriers is a significant–and exciting–challenge for water and wastewater utilities.
The lack of integration is broader than DER, with limited “integrated planning” across the water and energy sectors more generally. This is partly due to significant inter-sectoral differences, and a lack of a common language also hinders solutions–who in the water industry talks of drop function or voltage harmonic distortion? Another limiting factor is the global paucity of integrated training across the water-energy divide.
Help us improve integration of distributed energy systems
The Water Research Foundation and Water and Environment Reuse Foundation, are undertaking a study to understand and improve integration of distributed energy into water and wastewater utilities. The research is led by The University of Queensland, Australia and the survey will be open until 23 May 2017.
Take the survey now: https://remsurvey.rem.sfu.ca/DER4625/
For more information:
- Take the DER survey https://remsurvey.rem.sfu.ca/DER4625/
- Consider masters-level water-energy training https://www.uq.edu.au/study/program.html?acad_prog=5410offered through http://www.watercentre.org/
- Read about integrated water-electric utility planning http://www.waterrf.org/Pages/Projects.aspx?PID=4469
- Read about the DER project http://www.waterrf.org/Pages/Projects.aspx?PID=4625
- Contact Steven Kenway email@example.com