English Glossary

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on the horizontal


Voltage or current distortions that can be expressed by additional sinusoidals at frequencies that are integer multiples of the fundamental frequency.




Higher Calorific Value




high density polyethylene


Vertical change in elevation (SI unit: metres)

head-for-the-hills clause

Mandatory loan prepayment using insurance proceeds. Project credit agreements often provide that, if any of the major project facilities are destroyed or damaged and the project company subsequently receives a major insurnace recovery, then the borrower must use the insurance moneys to prepay the loan if the lenders so require.

heat exchanger

A device to transfer heat between two fluids without the fluids mixing or coming into contact with each other

heat meter

A device which measures thermal energy provided by a source or delivered, by measuring the flow rate of the heat transfer fluid and the change in its temperature (ΔT) between the outflow and return legs of the system.

heat pipe

A cylinder that transferes heat by convection of an inside gas or fluid

heat transfer efficiency

Useful heat output released/actual heat produced in the firebox.

heat transfer fluid

A fluid which can both transfer and store thermal energy (heat). Examples of heat transfer fluids are water, anti-freeze, thermal oil and molten salts.

heating demand

Energy needed annually (usually) for heating, measured in kWh/m²a or kWh/m3a.

heating load

The amount of heat that needed to be added to a building to maintain a comfortable temperature for its occupants.

heating value

The maximum amount of energy that is available from burning a substance.


A strategy that eliminates a risk through the spot sale of the risk or through a transaction in an instrument that represents an obligation to sell the risk in the future. The goal is to ensure that any profit or loss on the current sale or purchase will be offset by the loss or profit on the future purchase or sale.


The name for the high molecular weight polysaccharides which, together with cellulose and lignin, are contained in the cell walls of plants.


Son heteropolisacáridos (polisacárido compuesto por más de un tipo de monómero), formado por un conjunto heterogéneo de polisacáridos, que forman una cadena lineal ramificada. Entre estos monosacáridos destacan más: la glucosa, la galactosa o la fructosa.


((Hz) - The measure of frequency of a periodic phenomenon (1 Hz= 1 s–1). In alternating current grids all the generators are connected in parallel and run synchronously at the same frequency. During normal operation, the grid frequency varies slightly depending on the load on the grid. Synchronous frequency of large interconnected grids is 50 Hz (e.g. Europe) or 60 Hz (e.g. North America).

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