HKIE Professional Assessment - Energy Discipline key terms

A thermodynamic property combining internal energy with the product of pressure and volume, used to track heat flows in steady-flow devices such as boilers, turbines and heat exchangers.

The principle that entropy of an isolated system never decreases, so heat cannot flow spontaneously from cold to hot and no cyclic device can fully convert heat into work.

The maximum useful work obtainable from a system or energy stream as it reversibly reaches equilibrium with its environment, revealing where irreversibility destroys work potential in a plant.

The ratio of actual work output to ideal work for a turbine, or ideal to actual work for a compressor, when the process is compared with a reversible adiabatic reference.

The ideal vapour-power cycle of pump, boiler, turbine and condenser that models steam power plants; practical variants add reheat, regeneration and supercritical steam conditions.

The thermal energy input required per unit of electrical energy generated, usually expressed in kJ/kWh; it is the inverse of plant thermal efficiency and a standard performance benchmark.

A power plant arrangement where gas turbine exhaust heat raises steam for a bottoming steam turbine, achieving efficiencies well above either cycle alone.

Deliberate capture of waste thermal energy from processes, exhausts or condensers for reuse in space heating, hot water, preheating or another process stream.

The ratio of useful heating or cooling delivered to the energy input consumed by a heat pump or chiller; values above one are normal because ambient heat is moved, not created.

A rating of cooling output over a defined cooling season divided by electrical input over the same period, capturing part-load performance better than a single full-load efficiency figure.

A time series of energy demand at intervals such as half-hourly or hourly, used to size plant, assess part-load behaviour, and design tariffs or demand-response arrangements.

The maximum power drawn over a defined period; it drives network and generation capacity and often attracts maximum-demand charges on commercial electricity bills.

Planned utility or customer actions that reshape electricity use through efficiency, load shifting, curtailment or incentive programmes, reducing peak demand and improving system utilisation.

A systematic inspection and analysis of energy flows in a facility to establish consumption baselines, identify savings opportunities, and rank measures by cost and payback.

A documented process using agreed methods and baseline adjustments to quantify savings actually achieved by an efficiency measure after it is implemented.

A contractual arrangement where an energy service company finances or delivers efficiency improvements and is paid from, or guarantees, the resulting energy savings.

The constant unit price per kWh that would exactly recover all lifetime capital, operating and financing costs of a generating asset, allowing technologies of different scale and life to be compared.

A policy paying a fixed or premium price per unit of renewable electricity exported to the grid over a long contract, giving investors revenue certainty.

A tradable instrument representing the environmental attributes of one megawatt-hour of renewable generation, used for compliance or voluntary green-power claims.

A credit for a verified reduction or removal of greenhouse gas emissions elsewhere, used to compensate for emissions that cannot yet be eliminated at source.

A market where a cap is set on total emissions and allowances are traded, so participants with low abatement costs sell surplus permits to those facing higher costs.

The cost of reducing one additional tonne of emissions by a given measure, used to rank options and to compare a project against prevailing carbon prices.

The rate used to convert future cash flows to present value, reflecting the time value of money and project risk in investment appraisal.

The sum of discounted future cash inflows minus outflows over a project's life; a positive value indicates the project adds value at the chosen discount rate.

The share of incident solar irradiance converted into electrical output by a module, measured under standard test conditions and degraded by temperature and soiling in service.

Actual energy generated over a period divided by the energy the plant would produce at rated output continuously; it captures resource quality, availability and curtailment.

For a photovoltaic plant, the ratio of measured final yield to the yield expected from incident irradiation at standard conditions, isolating losses from resource variation.

A plot of turbine electrical output against hub-height wind speed, showing cut-in, rated and cut-out speeds used to estimate annual energy production from wind resource data.

A central plant producing chilled water that is distributed through insulated pipes to multiple buildings, gaining scale efficiency over individual building chillers.

The ratio of real power to apparent power in an alternating-current circuit; a low value increases current for the same useful power and attracts utility penalties.

Departure of a current or voltage waveform from a pure sinusoid caused by non-linear loads such as rectifiers and drives, leading to extra heating and equipment malfunction.

Regulatory requirements setting minimum thermal, lighting, equipment and control performance for new or altered buildings, verified at design and sometimes at completion.

Numerical modelling of a building's thermal and energy performance over a year using weather, construction, occupancy and system data, used for design comparison and code compliance.

The structured process of verifying that installed building services systems operate as designed and meet the owner's requirements, including testing, balancing and documentation.

A maintained record of identified project risks with assessed likelihood, impact, owner and mitigation action, reviewed regularly through the project life cycle.

A scheduling technique that identifies the longest sequence of dependent activities determining project duration, so float and delay impacts can be managed.

A formal study predicting the environmental consequences of a proposed project and setting mitigation and monitoring conditions before consent is granted.

A situation where an engineer's personal, financial or other interest could improperly influence professional judgement, requiring disclosure and where necessary withdrawal from the decision.

The professional obligation to inform relevant parties promptly when an engineer becomes aware of a risk to safety, health or the environment that others may not recognise.

Insurance covering a practising firm or engineer against claims of negligent advice, design error or breach of professional duty causing financial loss to a client.