US Wastes 61–86% Of Its EnergyAn updated analysis published last month by the Lawrence Livermore National Laboratory suggests that the USA is just 39% energy efficient. Put another way, more than half (i.e. 61%) of the energy that flows through our economy is ultimately wasted.
As has been the case for decades, most of the economy’s energy waste stems from electricity generation (because most power plants are relatively inefficient) and the transportation sector (internal-combustion vehicles are also notoriously inefficient, but they are getting better).
Feeling nostalgic for a time when the US economy used more energy than it wasted? You’ll have to go back to 1970. In that year, the country eked out a slightly better than 50% efficiency performance. Since 1970, however, the substantial growth in energy use for electricity and transportation — sectors that, as mentioned above, are historically poor at turning fuel into work — has caused energy waste to gradually prevail over energy productivity.
Fortunately, though, the nation is seeing a promising wave of technological advances, utility-sector innovation, behavioral science approaches, and policy breakthroughs that are helping to make energy productivity not just a serendipitous achievement in 1970, but an enduring reality for the decades ahead.
On the electric power generating side of the equation, using more cogeneration(CHP) or trigeneration seems like it would go along way to reducing this enormous amount of wasted energy.
CogenerationConventional central coal- or nuclear-powered power stations convert only about 33% of their input heat to electricity. The remaining 67% emerges from the turbines as low-grade waste heat. By capturing the excess heat, CHP uses heat that would be wasted in a conventional power plant, potentially reaching an efficiency of up to 80%, for the best conventional plants. This means that less fuel needs to be consumed to produce the same amount of useful energy.
A car engine becomes a CHP plant in winter when the reject heat is useful for warming the interior of the vehicle. The example illustrates the point that deployment of CHP depends on heat uses in the vicinity of the heat engine.
Cogeneration plants are commonly found in district heating systems of cities, hospitals, prisons, oil refineries, paper mills, wastewater treatment plants, thermal enhanced oil recovery wells and industrial plants with large heating needs. An example of cogeneration with trigeneration applications in a major city is the New York City steam system.
Thermally enhanced oil recovery (TEOR) plants often produce a substantial amount of excess electricity. After generating electricity, these plants pump leftover steam into heavy oil wells so that the oil will flow more easily, increasing production. TEOR cogeneration plants in Kern County, California produce so much electricity that it cannot all be used locally and is transmitted to Los Angeles.
"Micro cogeneration" is a so-called distributed energy resource (DER). The installation is usually less than 5 kWe in a house or small business. Instead of burning fuel to merely heat space or water, some of the energy is converted to electricity in addition to heat. This electricity can be used within the home or business or, if permitted by the grid management, sold back into the electric power grid. This recent development of small scale CHP systems has provided the opportunity for in-house power backup of residential-scale photovoltaic (PV) arrays. The results of a recent study show that a PV+CHP hybrid system not only has the potential to radically reduce energy waste in the status quo electrical and heating systems, but it also enables the share of solar PV to be expanded by about a factor of five. In some regions, in order to reduce waste from excess heat, an absorption chiller has been proposed to utilize the CHP-produced thermal energy for cooling of PV-CHP system. These trigeneration+photovoltaic systems have the potential to save even more energy and further reduce emissions compared to conventional sources of power, heating and cooling.
