Case 60: Water-based batteries

The market

The global battery market will reach nearly $74 billion in 2011. The Chinese market is the largest and fastest growing. The United States, for its part, accounts for approximately $15 billion in revenue for 15 billion batteries. High-end batteries are experiencing the strongest growth. The global market for materials used in battery manufacturing amounts to $3.8 billion annually. The added value generated from the metals extracted to create a finished product is almost one to twenty. Battery manufacturing and sales are definitely a profitable business. Although automotive batteries are almost 100% recycled, it is estimated that 40 billion batteries will end up in landfills this year. This means that approximately $2 billion worth of precious and rare metals will be discarded. While the first battery dates back two thousand years, it was Thomas Edison who created the first alkaline battery with a power output of 1 to 1.35 V. Today, the electrical power of batteries is measured in Joules (1 Joule = 1 Watt per second). One Watt-hour (Wh) therefore represents 3600 Joules. The global battery market has evolved considerably in recent years. Lead-acid batteries cost $0.17 per Wh. They are the cheapest and the ones that power cars. Nickel-cadmium batteries cost almost ten times more ($1.50). Lithium-ion batteries, on the other hand, are the standard used in Nissan electric vehicles at a cost of $0.47 per Wh. Few people realize that a kilowatt-hour of electricity produced by a battery can cost 100 to 500 times more than electricity from the grid. Society is willing to pay a high price for mobility. The largest energy storage battery was built by ABB in Fairbanks, Alaska. The enormous nickel-cadmium battery provides 40 MW, enough electricity to power 12,000 people for up to seven minutes. The smallest battery measures 2.9 mm by 1.3 mm, about the size of a pencil tip, and can be charged for 10 years.

Innovation

A major drawback of batteries is their weight. Lightweight batteries are a priority for the industry. Recharging batteries by pumping in a rechargeable electrolyte, instead of having to replace or recharge an entire unit, is another prominent innovation. The arrival of the vanadium-based battery, which can be recharged at least 10,000 times, is another breakthrough, even though the medium is in short supply to meet global demand. However, batteries are limited in terms of mining, recycling, and energy potential. One kilogram of crude oil yields 50 megajoules (MJ) of energy, while one kilogram of lead-acid batteries can only produce 0.1 MJ of electricity—500 times less. This explains why energy from batteries is so expensive and why recovering excess electricity from battery storage will always be at a competitive disadvantage. Weight for weight, even the best batteries in the world could theoretically only produce 6% of the energy that oil provides.

Professor Bo Nordell of Luleå University of Technology in Sweden has long been impressed by water's capacity to store heat. He studied thermal energy storage and discovered that one cubic meter of water can hold 334 MJ or 93 kWh of heat. The possibility of using ice, storing energy from the frozen winter months, or utilizing solar-heated water (see Case 53) represents an inexpensive storage mechanism that works very efficiently when applied on a large scale, with minimal infrastructure costs. There is no limit to the number of recharges. Professor Nordell supported Kjell Skogberg's doctoral thesis, which led to the construction of the world's first snow-cooling facility in Sundsvall, Sweden, for the town's main hospital, harnessing the coolness of snow collected during the winter.

The first cash flow

Per-Erik Larsson, the project manager appointed by the Västernorrland County Council, decided to design and operate the energy plant. In 2000, the main objective was to avoid the use of hazardous ozone-containing refrigerants, reduce electricity consumption, and capture winter snow, collected primarily from roads, roofs, and parking lots. As the snow melts, it flows through pipes. The design is quite simple: before the water reaches the hospital's pipes, it is filtered and passes through heat exchangers. The heat exchangers have a capacity of 3 MW and transfer heat from the hospital to the melted snow. The hospital water is cooled from 12 to 7 degrees Celsius. The heated cold carrier is then returned to the snow storage facility to melt more snow, which is then pumped back to the heat exchangers and the hospital to continue the cooling process. After installing the snow cooling system, the hospital reduced its electricity consumption for cooling by over 90%. This long-term solution has a minimum lifespan of 40 years, meaning the system will be recharged 40 times over 40 winter seasons. The inventors then founded Snowpower AB, which now commercializes this simple battery technology. The Sundsvall experiment is a large-scale application of the many smaller examples that have been developed using water as an energy storage medium. However, most of these systems used heat (instead of cold), but since the process works based on a temperature differential, it matters little whether the starting point is ice or hot water. Josef Jenni pioneered this in 1989 with the first solar house, and then again in 2005 with a solar tank containing 205 cubic meters of hot water, storing energy that can be converted into electricity. The city of Heerlen in the Netherlands was the first to use hot water in old, closed coal mines. Even though the deep mine provides water at 35 degrees Celsius, a series of heat exchangers is sufficient to meet all the heating needs in winter and cooling needs in summer for 350 homes and a shopping center. Water can retain five times more heat than concrete and is therefore an ideal alternative to batteries in large-scale operations.

The opportunity

Every home and every city has an elaborate water storage system. When we realize that heating and cooling the air and heating water account for 80% of a typical home's energy consumption, the real opportunity lies not only in choosing renewable energy sources but also in adopting the most efficient energy storage system. The cheapest and most abundant medium is water. This allows us to take a fresh look at the need for energy storage, since we can heat (or draw from cold water) and store it. The first advantage is that hot water eliminates the risk of bacterial contamination. In Spain, hotels must maintain all their water at 90 degrees Celsius to combat the proliferation of E. coli, only to then cool it down in a shower or bath to 38-40 degrees, losing more than 50% of the stored energy. If we apply the principle of "using what we have," heated water becomes a primary source of electricity. Semiconductor heat exchangers need only a 3-degree temperature difference to generate electricity, a phenomenon known as "thermoelectricity." The next time you take a shower, consider the wasted energy involved in mixing hot and cold water. At the same time, consider the potential if all existing water reservoirs could become energy storage tanks, transforming a passive service into an active component requiring a new type of smart grid. This presents so many entrepreneurial opportunities that it could well define the profession of "water electrician.".