Glossary

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BEIS: Department for Business, Energy & Industrial Strategy

ATEX: An EU directive (ATmosphere EXplosible) that describes the allowable equipment and working conditions in an environment with an explosive atmosphere

Blue hydrogen: Also known as grey hydrogen, this is hydrogen produced from natural gas but where the CO2 is captured and either stored underground or used to create new compounds (CCUS) and so can be described as ‘low carbon’ (see grey hydrogen)

Brown hydrogen: There’s actually no consensus on what defines brown hydrogen so better to avoid using the term

Cadent: The company Cadent Gas (National Grid)

CHP: Co-generation / combined heat and power

Coal gas: Flammable gaseous fuel made from coal. The composition varies according to the type of coal and carbonisation but typically comprises 50% hydrogen, 15% carbon monoxide, 30% methane and small amounts of other gases including carbon dioxide and nitrogen. (Also called Town gas)

Community trial: The is potential activity following the successful delivery of the Hy4Heat programme, whereby the gas network in an area (or a number of areas) will be converted to use of hydrogen. A ‘community trial’ includes changing over a number of households to use hydrogen appliances. Hy4Heat includes planning and preparing for a community trial (work package 9) but a decision to go to a community trial will be made by BEIS at a later date

Contract notice: Mandatory OJEU (official journal of the EU) notice that an ITT (invitation to tender document) is available. A contract notice is issued following a public information notice (PIN) being published

CCS / CCUS: Carbon capture and storage / carbon capture, usage and storage

Demonstration trial: This is Hy4Heat’s work package 8 and is where the hydrogen appliances (developed in work package 4) will be installed and demonstrated. It was previously referred to as an unoccupied trial

Dew Point: The temperature to which air must be cooled to become saturated with water vapour

Dual fuel appliance: An appliance that can run on both natural gas and hydrogen. In this context, it would likely be an appliance designed for hydrogen, but configured to initially utilise natural gas. This switch between the two could be through simply changing the gas supply, but more likely would be through the replacement of certain components (but where these were designed to facilitate such a switch)

EIP: Energy Innovation Portfolio

EMF: (Electromotive force) voltage developed by any source of electrical energy such as a battery or dynamo

Flame speed: Linear rate of expansion of the flame front in a combustion reaction

Flame failure device (FFD): A device to detect the presence (or lack of presence) of combustion. For hobs, ovens and fires this is typically a thermocouple in the flame, whilst for boilers this is an ionisation sensor

Flammability range: The concentration range which a flammable mixture of gas in air can be ignited at a given temperature and pressure. It is usually expressed in volume percentage

Green hydrogen: This is hydrogen produced from wind, solar or other renewable power via electrolysis, separating water molecules into hydrogen and oxygen molecules

Grey hydrogen: Grey hydrogen (sometimes called blue hydrogen) is produced from natural gas through steam methane reforming (SMR). This process is highly CO2 intensive. (See 'blue hydrogen)

GDNO: Gas Distribution Network Operators

H2-ready: An appliance that was designed for natural gas use, but with a change of components could then run on hydrogen gas. (Also called Switchable appliance)

Heat transfer coefficient: Proportionality constant between the heat flux and the thermodynamic driving force (temperature difference)

HHIC: Heating & Hotwater Industry Council

HSE: Health and Safety Executive

HSL: Health Service Laboratory

HSOP: Heat Strategic Options Project

Hydrogen embrittlement: The process by which metals such as steel become brittle and fracture due to the introduction and subsequent diffusion of hydrogen into the metal

Hydrogen only appliance: An appliance that is designed to be fuelled by hydrogen only and does not have dual fuel or switchable functionality

Light-back: Where the burning gas flows backwards through the burner ports. This occurs when the flame speed is greater than the unburnt gas speed

NDA-DRP: Nuclear Decommissioning Authority – Direct Research Portfolio

NOx: Generic term for the oxides of nitrogen

NPL: National Physical Laboratory

NGN: Northern Gas Networks

OJEU: Official Journal of the EU - an online platform that alerts suppliers to potential procurement opportunities

PIN: Prior Information Notice – optional OJEU notice to alert suppliers of a potential project

Prototype appliance: A certified, safe for use, hydrogen-fuelled appliance to be developed and delivered under Hy4Heat programme’s work package 4

Secondary air: Additional air that mixes into a combusting gas

SHFCA: Scottish Hydrogen & Fuel Cell Association

SMR: Steam methane reformation. A production process in which high temperature steam is used to produce hydrogen from a methane source, such as natural gas

STH: Solar to hydrogen

Switchable appliance: An appliance that was designed for natural gas use, but with a change of components could then run on hydrogen gas. (Also called H2-ready)

Town gas: Flammable gaseous fuel made from coal. The composition varies according to the type of coal and carbonisation but typically comprises 50% hydrogen, 15% carbon monoxide, 30% methane and small amounts of other gases including carbon dioxide and nitrogen. (Also called coal gas)

Tri-generation: This is the simultaneous generation of three forms of energy - heating, power and cooling

Volume manufacture: This refers to the scaling up of hydrogen-fuelled appliance manufacture beyond prototype levels, to be used in community trials, or wider conversion