Waste heat in the context of "Entropy"

Urban areas usually experience the urban heat island (UHI) effect; that is, they are significantly warmer than surrounding rural areas. The temperature difference is usually larger at night than during the day, and is most apparent when winds are weak, under block conditions, noticeably during the summer and winter.The main cause of the UHI effect is from the modification of land surfaces, while waste heat generated by energy usage is a secondary contributor. Urban areas occupy about 0.5% of the Earth's land surface but host more than half of the world's population. As a population center grows, it tends to expand its area and increase its average temperature. The term heat island is also used; the term can be used to refer to any area that is relatively hotter than the surrounding, but generally refers to human-disturbed areas.

Monthly rainfall is greater downwind of cities, partially due to the UHI. Increases in heat within urban centers increases the length of growing seasons, decreases air quality by increasing the production of pollutants such as ozone, and decreases water quality as warmer waters flow into area streams and put stress on their ecosystems.

Energy development is the field of activities focused on obtaining sources of energy from natural resources. These activities include the production of renewable, nuclear, and fossil fuel derived sources of energy, and for the recovery and reuse of energy that would otherwise be wasted. Energy conservation and efficiency measures reduce the demand for energy development, and can have benefits to society with improvements to environmental issues.

Societies use energy for transportation, manufacturing, illumination, heating and air conditioning, and communication, for industrial, commercial, agricultural and domestic purposes. Energy resources may be classified as primary resources, where the resource can be used in substantially its original form, or as secondary resources, where the energy source must be converted into a more conveniently usable form. Non-renewable resources are significantly depleted by human use, whereas renewable resources are produced by ongoing processes that can sustain indefinite human exploitation.

In economics, the secondary sector is the economic sector which comprises manufacturing, encompassing industries that produce a finished, usable product or are involved in construction.

This sector generally takes the output of the primary sector (i.e. raw materials like metals, wood) and creates finished goods suitable for sale to domestic businesses or consumers and for export (via distribution through the tertiary sector). Many of these industries consume large quantities of energy, require factories and use machinery; they are often classified as light or heavy based on such quantities. This also produces waste materials and waste heat that may cause environmental problems or pollution (see negative externalities). Examples include textile production, car manufacturing, and handicraft.

Complementary metal–oxide–semiconductor (CMOS, pronounced "sea-moss", /siːmɑːs/, /-ɒs/) is a type of metal–oxide–semiconductor field-effect transistor (MOSFET) fabrication process that uses complementary and symmetrical pairs of p-type and n-type MOSFETs for logic functions. CMOS technology is used for constructing integrated circuit (IC) chips, including microprocessors, microcontrollers, memory chips, and other digital logic circuits. CMOS overtook NMOS logic as the dominant MOSFET fabrication process for very large-scale integration (VLSI) chips in the 1980s, replacing earlier transistor–transistor logic (TTL) technology at the same time. CMOS has since remained the standard fabrication process for MOSFET semiconductor devices. As of 2011, 99% of IC chips, including most digital, analog and mixed-signal ICs, were fabricated using CMOS technology.

In 1948, Bardeen and Brattain patented an insulated-gate transistor (IGFET) with an inversion layer. Bardeen's concept forms the basis of CMOS technology today. The CMOS process was presented by Fairchild Semiconductor's Frank Wanlass and Chih-Tang Sah at the International Solid-State Circuits Conference in 1963. Wanlass later filed US patent 3,356,858 for CMOS circuitry and it was granted in 1967. RCA commercialized the technology with the trademark "COS-MOS" in the late 1960s, forcing other manufacturers to find another name, leading to "CMOS" becoming the standard name for the technology by the early 1970s. Two important characteristics of CMOS devices are high noise immunity and low static power consumption. Since one transistor of the MOSFET pair is always off, the series combination draws significant power only momentarily during switching between on and off states. Consequently, CMOS devices do not produce as much waste heat as other forms of logic, like NMOS logic or transistor–transistor logic (TTL), which normally have some standing current even when not changing state. These characteristics allow CMOS to integrate a high density of logic functions on a chip. It was primarily for this reason that CMOS became the most widely used technology to be implemented in VLSI chips.

A fossil fuel power station is a thermal power station that burns fossil fuel, such as coal, oil, or natural gas, to produce electricity. Fossil fuel power stations have machines that convert the heat energy of combustion into mechanical energy, which then powers an electrical generator. The prime mover may be a steam turbine, a gas turbine or, in small plants, a reciprocating gas engine. All plants use the energy extracted from the expansion of a hot gas, either steam or combustion gases. Although different energy conversion methods exist, all thermal power station conversion methods have their efficiency limited by the Carnot efficiency and therefore produce waste heat.

Fossil fuel power stations provide most of the electrical energy used in the world. Some fossil-fired power stations are designed for continuous operation as baseload power plants, while others are used as peaker plants. However, starting from the 2010s, in many countries plants designed for baseload supply are being operated as dispatchable generation to balance increasing generation by variable renewable energy.

Energy consumption is the amount of energy used. In physics, energy consumption refers to the transformation of energy from one form to another, rather than its complete disappearance. According to the law of conservation of energy, energy cannot be created or destroyed, only converted. For instance, when a light bulb "consumes" electricity, it is not destroying the electrical energy but rather converting it into light and heat. Similarly, a car "consumes" gasoline by converting its chemical energy into kinetic energy (motion) and heat. Understanding energy consumption is crucial for analyzing the efficiency of various systems and processes, as the ultimate goal is often to minimize the conversion of useful energy into less desirable forms, such as waste heat.

From a societal and economic perspective, "energy consumption" often refers to the use of energy resources by human civilization to power homes, industries, transportation, and other activities. This typically involves drawing upon various primary energy sources, including fossil fuels (coal, oil, natural gas), nuclear power, and renewable sources (solar, wind, hydro, geothermal). The scale and patterns of this consumption have significant implications for environmental sustainability, economic development, and geopolitical stability. Analyzing trends in global and regional energy consumption helps policymakers and researchers understand resource availability, greenhouse gas emissions, and the potential for transitioning to more sustainable energy systems.