Environmental Engineering Reference
In-Depth Information
environment. People living in cold and temperate climatic zones adapted by building
up stores of subcutaneous fat during summer and autumn. Those from tropical and hot
climates didn't require this annual energy buildup.
Civilisation began with humans' ability to store energy outside their bodies. By storing
food and fuel, we were able to maintain a constant supply of energy in a changing
environment. Over the last 200 years our capacity to store energy has, on the one hand,
been greatly enhanced and, on the other, been retarded by the increased use of fossil
fuels. Nature has already done the hard work of creating these energy stores, and we have
only needed to find ways of extracting and using the energy. Therefore, we have been
able to largely ignore the issue of large-scale energy storage until now. Even our most
sophisticated energy storage devices - electrical batteries - remained largely unchanged
until the late twentieth century. In fact, the earliest known model of rechargeable battery
- the lead-acid battery invented by Gaston Planté in 1859 - is still used in modern
automobiles.
Small-Scale Storage: Batteries
The first batteries bore little resemblance to the neat little slabs that slot into mobile phones
and other portable devices. In fact, the term 'battery' came into being because the earliest
such device, a row of Leyden jars used to store static electricity, reminded Benjamin
Franklin of a battery of cannon. All batteries work by converting chemical energy into
electrical energy. They consist of two parts, a cathode and an anode, each containing a
different chemical compound. The anode releases electrons, which are attracted towards
the cathode, creating an electrical current. In a lead-acid battery, the anode is made of
metallic lead and the cathode of lead dioxide. The acid merely acts as a medium through
which current can flow. Dry batteries, such as those used in laptop computers and mobile
phones, generally use metals and oxides as anodes and cathodes.
Great strides have been made in electricity storage in the last thirty years, as battery
technology has adapted to suit an ever-increasing array of electronic devices. Yet batteries
remain capable of storing only relatively small amounts of energy. In 2012 the State Grid
CorporationofChina,incollaborationwiththeelectriccarmanufacturerBYD,unveiledthe
world's largest battery, capable of storing 36 megawatt-hours of electricity. This facility is
larger than a football field and cost $500 million (U.S. million) to build. When we consider
that a small 500-megawatt coal-fired power plant costs about the same amount to build,
yet produces 36 megawatt-hours every four minutes, it becomes clear that electrical energy
storage is not even close to industrial scale yet.
