Paragraph 9 General principles for the calculation of electricity from cogenerationF1

(1)

Values used for the calculation of efficiency of cogeneration and primary energy savings for units other than micro-cogeneration units are to be determined on the basis of the expected or actual operation of the unit under normal conditions of use.

(2)

For micro-cogeneration units the calculation may be based on certified values.

(3)

Electricity production from cogeneration is to be considered equal to total annual electricity production of the unit measured at the outlet of the main generators for—

(a)

high efficiency cogeneration units falling under sub-heads (ii), (iv), (v), (vi), (vii) and (viii) in paragraph 5(b) of this schedule with an annual overall efficiency of at least 75%,

(b)

high efficiency cogeneration units falling under heads (i) and (iii) of paragraph 5(b) with an annual overall efficiency of at least 80 %.

(4)

For cogeneration units with an annual overall efficiency below that specified in sub-paragraph (3), cogeneration is to be calculated according to the following formula—

E_{C H P} = H_{C H P} \times C

(5)

In sub-paragraph (4)—

(a)

E_CHP is the amount of electricity from cogeneration,

(b)

C is the power to heat ratio,

(c)

H_CHP is the amount of useful heat from cogeneration, calculated for this purpose as total heat production minus any heat produced in separate boilers or by live steam extraction from the steam generator before the turbine.

(6)

Where actual power to heat ratio is not known for the high efficiency cogeneration units listed in Table 2, the default power to heat ratio values in Table 2 may be used where the calculated cogeneration electricity is less or equal to total electricity production of the unit—

Table 2

Type of Unit	Default power to heat ration, C
Combined cycle gas turbine with heat recovery	0.95
Steam back pressure turbine	0.45
Steam condensing extraction turbine	0.45
Gas turbine with heat recovery	0.55
Internal combustion engine	0.75

(7)

Where a share of the energy content of the fuel input to the cogeneration process is recovered in chemicals and recycled this share can be subtracted from the fuel input before calculating overall efficiency in sub-paragraphs (3) and (4).

(8)

SEPA may determine the power to heat ratio as the ratio of electricity to useful heat when operating in cogeneration mode at a lower capacity using operational data of the specific unit.

(9)

SEPA may use reporting periods other than annually for the purpose of calculating overall efficiency in sub-paragraphs (3) and (4).

Annotations

Textual amendments

F1: Sch. 25 inserted (1.11.2025) by The Environmental Authorisations (Scotland) Amendment Regulations 2025 (S.S.I. 2025/165), reg. 1(2), sch. 16 (with sch. 23)