Deflections of plating in between supporting grillage.

Heating, ventilation, and air conditioning

High voltage alternating current.

High voltage direct current.

Converts electric power from high voltage alternating current (AC) to high-voltage direct current (HVDC), or vice versa

A specialised type of substation which forms the terminal equipment for a high-voltage direct current (HVDC) transmission line. It converts direct current to alternating currentor the reverse, They are land based facilities and offshore structures for offshore wind farms.

A two fluid reactor that has thorium in the fuel salt is sometimes called a "one and a half fluid" reactor, or 1.5 fluid reactor.

Hybrid nuclear fusion–fission is a proposed means of generating power by use of a combination of nuclear fusion and fission processes.

Power plants where a combination of energy sources to make a process more efficient or and less damaging to the environment.

Hybrid renewable energy systems are becoming popular as stand-alone power systems for providing electricity in remote areas due to advances in renewable energy technologies.

The terminal point of a water main with fittings for the attachment of a hosepipe.

Hydraulic fracturing, also called fracking, fracing, hydrofracking, fraccing, frac'ing, and hydrofracturing, is a well stimulation technique involving the fracturing of bedrock formations by a pressurized liquid.

A proppant is a solid material, typically sand, treated sand or man-made ceramic materials, designed to keep an induced hydraulic fracture open, during or following a fracturing treatment.

Hydraulic head or piezometric head is a specific measurement of liquid pressure above a vertical datum.

A device which converts hydraulic fluid power into mechanical force and motion. It usually provides rotary motion.

A mechanism for driving hatch covers to the open or closed position. It uses a hydraulic motor attached to the coaming to power a pinion which drives a rack fitted to the panel.

Hydraulics is a technology and applied science using engineering, chemistry, and other sciences involving the mechanical properties and use of liquids.

Compounds containing hydrogen, fluorine, chlorine, and carbon atoms. Although ozone depleting substances, they are less potent at destroying stratospheric ozone than chlorofluorocarbons (CFCs).

The method used for cleaning of the surface to be repaired. The degree of cleaning depends on the pressure of the water jet.

A hydrocarbon is an organic compound consisting entirely of hydrogen and carbon.