Water Journal : Water Journal December 2011
conference reviews water DECEMBER 2011 49 Unlike energy projects for which customers were prepared to pay for supply, water customers persisted in the view that water should be free or low cost. As a result, commercial suppliers of water are ever inclined to keep costs low so as to maintain relationships with them. This means that they are not able to offer the same level of returns on water projects to funding bodies, with the consequence that water projects are less attractive to those seeking a reliable and increasing return. A series of panellists followed, with the highlight being the comments by Graham Dooley, who focused on the financing difficulties experienced by smaller plants. He pointed out that there was a perception of capital scarcity in Australia (because of the issues previously identified by Ghassan Ejjeh) associated with the returns available to funding bodies from comparable infrastructure investments. Graham quoted a 15% internal rate of return (IRR) for water projects competing against 35% and above for mining-related infrastructure. He pointed to the special funding difficulties faced by small water projects, which are inherently more risky to the financier, and which were turning to seek equity partners who would share project risks and funding. He identified three forms of equity being considered: • Include partners with strong balance sheets in return for giving up equity in the project; • Private equity finance with entities such as superannuation funds, which are looking for better returns than those offered by bonds. For these partners, the risk equation has to be structured to suit them, not the technology and its limits; this puts an understandable pressure on project participants, which can actually produce a superior outcome; • Bundling projects -- a number of smaller projects with mixed sizes and risk profiles are put together into a package which is more attractive to banks. Energy Sources, Uses and Efficiency Session Energy recovery from the SWRO brine stream has been one of the most sensational advances in seawater desalination in the last decade. This innovation greatly contributed to improved sustainability of water solutions, decreased energy and carbon footprint and decreased water cost. Energy footprint is now one of the major challenges for seawater desalination. This segment of desalination technology is in constant development and is a key to high efficiency, reliable performance and successful operation of SWRO processes. One of the most interesting and potentially valuable initiatives discussed was a paper by a Japanese team on Solar Thermal Energy Seawater Desalination (authors: Toru Kannari, Yoshiaki Miho, Yuji Saito, Dr Rencai Chu, Professor Yoshiharu Horita). Toru Kannari, who delivered the presentation, began by backgrounding the difficulties associated with delivering desalinated seawater using solar energy. These range from problems with constructing and maintaining solar facilities to those associated with fine-tuning operations and building stability into the system. Having identified current limitations, Mr Kannari then moved to describe a promising new solution to raise the operating efficiency of solar desalination systems by way of the addition of a thermoelectric generator (TEG) module. In this configuration, solar heat is collected and concentrated in the solar thermal collector and used to generate steam, which is then employed as the heat source for the thermal desalination unit. To optimise the system, TEG modules are attached across almost the entire surface of the heat exchange wall of the steam generator. A TEG module is composed of multiple elements, each of which consists of two different semi-conducting materials connected as a "thermocouple" to convert heat directly into electricity. The vaporisation system used in this configuration can concurrently generate steam and electricity without the need for a steam turbine generator. Part of the electricity generated by the TEG module is used for operating the heat desalination unit and the surplus electricity generated can be supplied directly to the grid or to the RO desalination plant for further production of water. Since the system has no moving parts, is easy to operate and highly reliable, it is expected to be invaluable for satellite systems of 5,000 or 20,000 tons/day capacity. Furthermore, the combination of this TEG technology with a trihybrid NF/RO/MED is expected to be more efficient in the utilisation of heat and electric power, and is considered to be one of the most suitable systems for next generation seawater desalination plants driven by solar thermal energy. Intakes and Outfalls Session Seawater intake design needs to adapt to increasing environmental sensitivity applied to desalination projects worldwide, and new technologies are developing in order not only to improve seawater abstraction reliability and quality of the seawater feed, but also to improve the environmental impact associated with the seawater abstraction and discharge. Seawater abstraction systems are of vital importance and are a major contribution to desalination costs and reliability of operation. Delegates enjoy an Australian cultural evening.
Water Journal April 2012
Water Journal November 2011