Definitions - p


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Parallel Strand Lumber

Beams made from strands of wood fiber mixed with resins and pressed into large beams.

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Parallel Wiring

This is when a group of electrical devices, such as PV modules, are wired together to increase ampage, whilst the voltage remains constant.

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In climate modeling, this term refers to the technique of representing processes that cannot be explicitly resolved at the resolution of the model (sub-grid scale processes) by the relationships between the area averaged effect of such sub-gird scale processes and the larger scale flow.

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Passive House

A Passive House is a house designed to use Passive Solar Design principals to drastically reduce its energy demands by making full use of the energy supplied by the Sun, this thereby reduces ecological footprint of the building.

This can include its orientation, window placement, Trombe Walls, ventilation, thermal mass and living space placement. It also include the adoption of standards on energy efficiency to further reduce energy demands.

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Passive Solar

Passive solar design refers to the use of the sun's energy for the heating and cooling of living spaces. With this approach, the building itself or some element of it takes advantage of natural energy characteristics in materials and air created by exposure to the sun.

Passive systems are simple, have few moving parts, and require minimal maintenance and require no mechanical systems. Often the thermal characteristics of materials are extensively used, often termed as Thermal Mass design.

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Passive Solar Design

Passive Solar Design is undergoing a resurgence as more people not only recognise the comfort benefits and lower energy bills of solar architecture, but now see a way of helping reduce the polluting effects of green house gases through less reliance on fossil fuels for heating and cooling.

Basic house design principles include:
  • Orientation of the main living areas towards the North (or South if in the Northern hemisphere)
  • Glazing used to trap the warmth of the Sun.
  • Thermal mass to store the heat from the Sun.
  • Insulation to reduce heat loss or heat gain.
  • Ventilation to capture cooling breezes.
A well designed solar home should remain within 18 degrees C to 28 degrees C throughout the year and save 60% to 70% in average household heating costs.

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Passive Solar Energy

Passive Solar Energy is the energy captured by a building from the Sun and used to either heat or cool a building.

The heating is usually a direct mechanism, where as the cooling is done by using the Sun's energy to help displace heat within a building, for instance by 'sucking' air through a property using a roof ventilation system.

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Passive Solar Heating

Passive solar heating is one of several design approaches collectively called passive solar design. When properly combined, these strategies contribute to the heating, cooling, and day lighting of nearly any building. The types of buildings that benefit from the application of passive solar heating range from houses to large office facilities.

Passive solar heating typically involves:
  • Solar energy collection through properly-oriented, south-facing windows.
  • Storage of this energy by "thermal mass," which are building materials with high heat capacity such as concrete slabs, brick walls, or tile floors.
  • Distribution of the stored solar energy back to the living space, as required, via the mechanisms of natural convection and radiation.
  • Window specifications to allow higher solar heat gain coefficient for Solar facing glazing.
Passive solar heating systems do not have a high initial cost or long-term payback periods, both common with many active solar heating systems. 

Another benefit to passive solar heating is increased comfort: if properly designed, passive solar buildings are bright and sunny and in tune with climate and nature. As a result, there are fewer fluctuations in temperature, resulting in a higher degree of temperature stability and thermal comfort.

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Passive Ventilation

Passive ventilation is a natural ventilation system that makes use of natural forces, such as wind and thermal buoyancy, to circulate fresh air to and from an indoor space. 

Such passive ventilation systems work to regulate the internal air temperature as well as bring fresh air in and send stale air out.

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Peak Sun Hours

This is the equivalent number of hours per day when solar irradiance averages 1,000 w/m2. For example, six peak sun hours means that the energy received during total daylight hours equals the energy that would have been received had the irradiance for six hours been 1,000 w/m2. A term often used in association with solar panels.

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Perfluorocarbon (PFC) is a powerful greenhouse gas emitted during the production of aluminum.

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Perfluorooctanic Acid

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Persistent Pesticides

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Phantom Load

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Photochemical Smog

Air pollution caused by chemical reactions of various pollutants emitted from different sources.

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Used in vinyl products to make them softer and more flexible; also in cosmetics, fragrances, food wraps, and other products. In baby boys, exposure to phthalates can likely increase the risk of birth defects and hormone changes. In men, they likely increase the risk of reproductive problems and hormone changes. The U.S. government regulates industrial discharges of phthalates, but they are unregulated in food products, cosmetics, and consumer and medical products.

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Physiographic Region

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Planned Obsolesence

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Plant Association

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Plate Tectonics

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Plug-in Hybrid

Also known as Plug-in Hybrid Electric Vehicles (PHEVs), plug-in hybrids are similar in design to conventional Hybrids except their battery can be recharged from an external power source such as electric vehicle charging points.

As a result they can travel significant distances, typically 40 miles, using just their electric motor before their internal combustion engine kicks in.

They are being widely touted as a means of cutting carbon emissions and urban air pollution, while improving vehicle fuel efficiency to a level where cars can travel upwards of 250 miles on a single tank of fuel.

A range of new plug-in hybrids are expected to be launched over the next two years, including GM's Chevy Volt and a new version of Toyota's Prius.

Plug in hybrids are expected to be more expensive than conventional cars, however they will result in reduced fuel costs and a number of governments are offering tax breaks to try and increase consumer take up.

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Polar Air Mass

A cold air mass that forms in a high-latitude source region.

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Pollution Prevention

Reducing the amount of energy, materials, packaging or water in the design, manufacturing or purchasing of products or materials in an effort to increase efficient use of resources, reduce toxicity and eliminate waste.

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Polybrominated Diphenyl Ethers

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Polyculture is agriculture using multiple crops in the same space, in imitation of the diversity of natural ecosystems, and avoiding large stands of single crops, or monoculture. It includes crop rotation, multi-cropping, intercropping, companion planting, beneficial weeds, and alley cropping.

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Post Consumer Waste

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Postmodern Science

Postmodern Science is a 'branch' of postmodernism.

Postmodernism is "post" because it is denies the existence of any ultimate principles, and it lacks the optimism of there being a scientific, philosophical, or religious truth which will explain everything for everybody - a characterisitic of the so-called "modern" mind. The paradox of the postmodern position is that, in placing all principles under the scrutiny of its skepticism, it must realize that even its own principles are not beyond questioning. As the philospher Richard Tarnas states, postmodernism "cannot on its own principles ultimately justify itself any more than can the various metaphysical overviews against which the postmodern mind has defined itself."

Basically, postmodern science shies away from trying to create a 'unified truth' and rather focuses on the here and now and what is can be 'deduced' from that. The trouble is this leads to science by agreed consensus of observation and trust - rather than the traditional scientific approach of knowledge advancement by experimentation and proving of a hypothesis - i.e. the scientific method

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Power Conversion Efficiency

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Power Pool

An association of interconnected electric systems in a region, often having an agreement to coordinate operations and plans for reliability improvements.

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Precambrian Rock

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Precautionary Approach

The approach promoted under the Framework Convention of Climate Change to help achieve stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous interference with the climate system.

Note: In essence this is the 'just in case' approach; the trouble with it is it assumes the cost of doing something is essentially 'free' compared to the future cost of not doing something. Rather the opportunity cost of doing something regardless is not clearly taken into account (i.e. could the money being spent now on inefficient energy sources to combat climate change have been better spent on further energy research that could ultimately lead to no real environmental pollution at all?)  Everything has a cost.

Also the precautionary approach 'weakens' the need for more rigorous scientific principal based research; i.e. you just need to show (and not truthfully prove) a possible outcome to give support to the precautionary approach.

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The tendency of the Earth's axis to wobble in space over a period of 23,000 years. The Earth's precession is one of the factors that results in the planet receiving different amounts of solar energy over extended periods of time.

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Prescribed Burning

Deliberate setting and careful control of surface fires in forests to help prevent more destructive fires and to kill off unwanted plants that compete with commercial species for plant nutrients; may also be used on grasslands. Also known as 'back burning'.

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Prevailing Wind

The wind direction most frequently observed during a given period.

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Price Preference

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Primary Consumer

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Primary Energy

Energy embodied in natural resources (e.g. coal, crude oil, sunlight, uranium) that has not undergone any anthropogenic conversions or transformations.

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Primary Sector

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Proxy Climate Indicators

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PV Module

A PV module is basically a solar photovoltaic module used in converting Sun light into electrical energy. They are usually manufactured as a sealed unit with a given output voltage and wattage rating. They are often grouped together to create a larger total power output. 

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