Boxed Text

Example

<boxed-text id="bk978-0-7503-2304-8ch1box1" orientation="portrait" position="float">
  <label>Box 1.1.</label>
  <caption>
    <p>Units and terms</p>
  </caption>
  <p>‘Power is often confused with ‘energy’, and is also often used to mean
‘electricity’, whereas the latter is only one form of energy; heat and transport
fuels are others.’</p>
  <p>The <bold>power</bold> of an energy device is measured in <bold>watts</bold> (W)
and multiples of watts: kilowatts (1 kW = 1000 W) megawatts (1 MW = 1000 kW),
gigawatts (1 GW = 1000 MW) and terawatts (1 TW = 1000 GW). A large wind turbine
might have a full power rating or ‘generating capacity’ of 5 MW, the figure for a
large conventional power station might be 1 GW, for a kettle, 1–2 kW.</p>
  <p>Although wind turbines, nuclear power plants or whatever, are often called energy
  <italic toggle="yes">generating</italic> devices, strictly they are energy <italic toggle="yes">conversion</italic> devices, converting one form of energy into
  another, with, inevitably some losses. Thermal energy generating capacity is
  differentiated from electricity capacity by adding ‘th’ or ‘e’, respectively (in
  brackets), after the power figure, e.g. MW (e). Note that the rated power capacity
  figure only indicates what the device could produce if it was able to work at full
  power output. In practice it will usually not be able to do that, for example given
  the variability of renewable sources like wind and solar, but also due to
  breakdowns, maintenance periods and so on. So, as I will be illustrating, the actual
  available generating capacity with be some fraction of the so-called ‘nameplate’
  power rating capacity: see table <xref ref-type="table" rid="bk978-0-7503-2304-8ch2t2">2.2</xref> and figure <xref ref-type="fig" rid="bk978-0-7503-2304-8ch2fig8">2.8</xref> in chapter <xref ref-type="book-part" rid="bk978-0-7503-2304-8ch2">2</xref> for some typical <italic toggle="yes">Load
Factors</italic>, reflecting the amount of energy that devices can actually
deliver.</p>
  <p>The amount of <bold>energy</bold> a device generates or uses (that is, converts
from one form of energy to another) depends on its rated power level and on the
length of time it is operating at that level, so it is calculated as watts × time.
The units of energy are kilowatt-hours (kWh), megawatt-hours (MWh), and so on in
1000 Wh multiples (e.g. GWh and TWh).</p>
  <p>The kilowatt hour is the unit used for selling electricity, so it should be
familiar. I have (mostly) avoided the less familiar Joule (J), though exajoules, 10
to the power 18 joules, are used for some large quantities. To convert: Watts =
Joules/s, so 1 kWh is 3 600 000 J and 1 megajoule is 278 MWh. Exajoules (EJs) are
inescapable in the biomass section, since that covers biomass used for a range of
purposes—heat and transport as well as power.</p>
  <p>Some common technical <bold>abbreviations</bold> used:<def-list list-content="abbreviations">
    <def-item>
      <term>AC</term>
      <def>
        <p>Alternating current</p>
      </def>
    </def-item>
    <def-item>
      <term>AD</term>
      <def>
        <p>Anaerobic digestion</p>
      </def>
    </def-item>
    <def-item>
      <term>CCS</term>
      <def>
        <p>Carbon capture and storage</p>
      </def>
    </def-item>
    <def-item>
      <term>CCGT</term>
      <def>
        <p>Combined cycle gas turbine</p>
      </def>
    </def-item>
    <def-item>
      <term>CHP</term>
      <def>
        <p>Combined heat and power</p>
      </def>
    </def-item>
    <def-item>
      <term>CO<sub>2</sub>
    </term>
      <def>
        <p>Carbon dioxide</p>
      </def>
    </def-item>
    <def-item>
      <term>CSP</term>
      <def>
        <p>Concentrating solar power</p>
      </def>
    </def-item>
    <def-item>
      <term>CPV</term>
      <def>
        <p>Concentrating photo-voltaics</p>
      </def>
    </def-item>
    <def-item>
      <term>HVDC</term>
      <def>
        <p>High-voltage direct current</p>
      </def>
    </def-item>
    <def-item>
      <term>OWC</term>
      <def>
        <p>Oscillating water column</p>
      </def>
    </def-item>
    <def-item>
      <term>P2G</term>
      <def>
        <p>Power to gas</p>
      </def>
    </def-item>
    <def-item>
      <term>PV</term>
      <def>
        <p>Photovoltaic (solar)</p>
      </def>
    </def-item>
    <def-item>
      <term>SRC</term>
      <def>
        <p>Short rotation coppice</p>
      </def>
    </def-item>
  </def-list>
</p>
  <p>Some other abbreviations:<def-list list-content="abbreviations">
    <def-item>
      <term>BEIS</term>
      <def>
        <p>UK Department of Business Energy and Industrial Strategy</p>
      </def>
    </def-item>
    <def-item>
      <term>DECC</term>
      <def>
        <p>UK Department of Energy and Climate Change</p>
      </def>
    </def-item>
    <def-item>
      <term>EU</term>
      <def>
        <p>European Union</p>
      </def>
    </def-item>
    <def-item>
      <term>FIT</term>
      <def>
        <p>Feed-In Tariff</p>
      </def>
    </def-item>
    <def-item>
      <term>NGO</term>
      <def>
        <p>Non-governmental organisation</p>
      </def>
    </def-item>
    <def-item>
      <term>MENA</term>
      <def>
        <p>Middle East North Africa</p>
      </def>
    </def-item>
  </def-list>
</p>
  <p>
  <bold>References</bold> All the web links were checked and were live in March 2019,
with, in the case of ongoing sites, the most recent year of live posts cited.</p>
</boxed-text>