(1) Without prejudice to any other relief from tax which may apply, and subject to such conditions as may be prescribed or otherwise imposed, a full relief from tax shall be granted on any natural gas which is shown to the satisfaction of the Commissioners to have been supplied for use -

(a) solely for the generation of electricity,

(b) for chemical reduction or in electrolytic or metallurgical processes,

(c) under diplomatic arrangements in the State,

(d) for heat and power cogeneration (other than heat and power cogeneration by a micro-cogeneration unit within the meaning of Directive 2012/27/EU of the European Parliament and of the Council of 25 October 2012 [OJ No. L315, 14.11.2012, p.1]), where it is determined, by a competent authority designated for the purpose by the Minister for Finance, that such cogeneration meets the requirements for high-efficiency cogeneration under Directive 2012/27/EU of the European Parliament and of the Council of 25 October 2012,

(e) in the production of horticultural produce in one or more than one glasshouse of a total area of not less than a quarter of an acre, or