Supplement to GLIAS Newsletter 106, October 1986
From the 1890s there were many schemes to generate electricity with steam produced from the combustion of refuse. This report gives the background to one of these schemes and describes what was still to be seen on 17th May 1986 when the site was visited by members of the GLIAS recording group.
The installation, completed in 1897, was in fact the first successful 'combined' station not converted from an existing refuse destructor. Its design was reported and discussed extensively at professional meetings and in the technical press, raising controversy over whether such an undertaking could be made effective enough to repay a higher-than-usual level of capital investment.
HISTORY OF THE INSTALLATION
The Vestry of the Parish of St. Leonard, Shoreditch, originally undertook to supply electricity to prevent a monopoly falling into the hands of private electric lighting companies which had applied direct to the Board of Trade for Provisional Orders to supply the area after the Vestry had rejected their plans. In September 1891 the Vestry decided to obtain powers to supply electricity for public and private purposes, the Board of Trade granting a Provisional Order in July 1892.
At the time, the Vestry was considering a refuse destructor as a more cost-effective way of disposing of 20,000 tons of rubbish p.a. than barging it away. They engaged E Manville, consulting engineer, as advisor for the electricity supply station. He recommended combining the two services, advising that the steam required for the estimated electrical output could be got from a properly designed destructor, without need of other fuel.
Manville's proposal was adopted by the Vestry in February 1893. Estimates showing the heavy capital outlay caused much hesitation on the Vestry's part and not until the 1894 election, when the ratepayers completely endorsed the scheme, was agreement reached to proceed.
Because the destructor/generator was part of a larger undertaking, great difficulty was experienced in finding a suitable site and it was not until 1895 that tenders for the work were being requested and received.
Offices north from Hoxton Square
The combined station, officially inaugurated by Lord Kelvin on 28th June 1897, consisted of a destructor house 80 feet square with a 150ft chimney, an engine house and offices.
Because space was at a premium, the refuse collected by the rubbish carts was not delivered in the usual way up an inclined roadway. Instead each cartload, after weighing (for the calculation of running costs) was emptied into one of two hoppers mounted on electric lifts. Each hopper, on its electrically-operated bogie, was elevated to the level of a platform above the destructor cells. There, electrical connection was made manually to two overhead wires and the bogie moved along rails until it reached its required position. If the refuse was not needed immediately, it was dropped into a 60-ton capacity storage bin until required and only then discharged into the special charging trucks, designed by Boulnois and Brodie.
The trucks, of a square-box pattern, had five compartments each holding a cartload of refuse (about 5cwt), enough for one charge of each furnace. Each charge was dropped through a horizontal door onto the inclined drying hearth and thence into the furnace.
There were 12 destructor cells, with a grate area of 25 sq. ft. each and between each pair was a Babcock and Hillcox water tube boiler. Each cell had both steam and forced-air draught, the latter provided by three electrically driven Sturtevant fans, each designed to give 8,000cu.ft. of air per minute, allowing temperatures of 2,000°F to ensure rapid and thorough combustion of the refuse and destruction of all odours. The clinker residue was used to make paving slabs. Gases from the cells passed immediately to the boilers, which could also be fired by coal at periods of peak demand — ordinary fire-bars were provided under each boiler.
The final feature of the destructor scheme was a Druitt Halpin thermal storage system, whereby the steam generated continually through the day was used to heat boiler feedwater in a cylindrical tank 35ft long and 8ft in diameter, though, surprisingly, uninsulated. This tank was connected at the top with the main steam pipe and worked at the same pressure and temperature as the boilers.
The generating plant consisted of three Willans & Robinson 300hp triple expansion engines each coupled to an Electric Construction Co. 165kW 1100 V DC dynamo and three Willans & Robinson 120hp triple expansion engines, each coupled to an E.C.C. 70 kW, 165v DC dynamo, giving a total engine capacity of 1,260hp developing 705 kW.
Steam pressure varied between 120 and 200 psi with adjustable valve gear. The exhaust steam from the engines was economically used for heating the slipper baths, swimming pool and public library built as part of the same undertaking. There was also a novel 60kW, 1100/165 volt variable ratio motor generator to balance the supplies to the high and low voltage circuits and a battery of accumulators to boost the supply by 30 to 50 KW. The 1100 V supply was transmitted to three sub-stations where rotary transformers supplied 150 V DC to a wire distribution system. The public lighting consisted of 57 standards supporting double-carbon arc lamps, automatically replaced at midnight by two 32 c.p. incandescent lamps sited on the same posts. The charges for private consumption of electricity were made according to the Wright demand indicator system.
The enthusiasm of the Vestry for its new electric power was considerable and it was the first local authority to provide electric light to artisan housing, in its 1899 Nile Street flats. In 1898, three Belliss engines with 250kW generators were added to the high tension system, bringing the total output to 1455KW. Demand for electricity soon outstripped what the destructor's steam could generate; a coal-fired station was built beside the Regent's Canal in 1902, in 1914 a 6,600 V 3-phase A/C was connected from Stepney and by 1923 the Coronet Street station had been converted to a distribution centre, with 7,000kW of rotary converters. The 3 Belliss engines, relocated, remained useable, eg during the coal crisis of 1947. The destructor remained in operation until with declining coal-ash content of refuse it was probably no longer efficient; by 1953 its shell had been converted to a garage. The converter station, nationalised in 1948, remained in use until the 1960s.
The Shoreditch scheme, whilst not the first attempt to produce electricity from refuse, was the first successful purpose-designed installation. This was partly because of the high calorific value of the area's refuse, making steam generation more effective than usual, to careful engineering design and because the Vestry's large population with many small businesses, not to mention 300 pubs, provided the perfect outlet for electricity sales. Costings indicate, however, that electricity production was only a remunerative by-product of expensive refuse disposal.
Cross section of generator/refuse destructor in 1897 (above); ground floor layout of site (below)
FEATURES SURVIVING MAY 1986
The following describe the buildings as seen in May 1986, before the start of works by Hackney Borough Council to convert them to studios and workshops.
MACHINE HALL
The 'Machine Hall' was originally the main electricity generating room. The room was 46ft east-west and 68ft north-south. It was c.28ft high to the eaves.
In the centre of the east wall was an 8ft x 10ft high sliding door into the yard, to bring the machinery into the hall. All other doorways were of pedestrian size. Light wrought-iron trusses supported a matchboarded and slated roof with a ventilated clerestory and two lines of skylights. Through the north wall was a fire-proof door leading to an annexe (not investigated; but possibly the later site of the Belliss generator sets). In the south wall was a door into the corridor and staircase of the main offices and also an entrance to the gallery at first floor. A small door in the west wall led to the light well and another to the EHT room.
Along the west wall was a steel-framed gallery cantilevering over cast-iron columns, approximately 8ft above floor level and approached by a central flight of steps. An elegant wooden balustrade remained for half the length of the gallery. There were control panels for the rotary converters, overlooking the machine floor and traces of earlier control equipment to the rear of the gallery. Running along the length of the machine hall was a 5 ton hand-operated overhead crane by Smith of Rodley for the installation and maintenance of the machinery. In the floor of the hall there were reinforced concrete pits, probably the foundations of the 7,000 kW rotary converters. The floor was paved with red and grey quarry tiles, laid in patterns around the pits and evidently contemporary with the conversion to a substation in the 1920s. No evidence of the steam pipes etc. of the earlier generating plant remained. There were two large cable trenches running from north to south and others running from east to west. These trenches were covered by standard chequer plate flooring. They had brackets on the walls and stacks of ceramic spacers located on vertical pins, to support cables. From them cable ducts led to the rotary converter foundation pits, some with 12 ways each 4in x 4in and some with 24 ways each 6in x 4in.
Generator hall looking north
THE EXTRA HIGH TENSION (E.H.T.) BUILDING
West of the machine hall was a small building of two tall storeys plus basement with fire-resistant concrete jack arch floors on steel beams. On the ground floor were 2 stacks (4 rows) of back-to-back cubicles formed of ceramic concrete Blabs, with similarly constructed shelving above for busbars mounted on porcelain insulators, all arranged in triplicate for a 3-phase supply and probably designed to prevent flash-over between high-voltage switch — or trip — gear, which had been removed. The room above had held free-standing electrical equipment. Both rooms had funnel-shaped outlets for a carbon-dioxide fire extinguishing system. This was fed from gas cylinders in the basement, with valves actuated by weighted cables with fusible links.
OFFICES
The office accommodation facing Coronet Street had an impressive façade with lunette windows and the motto 'E Pulvere Lux et Vis' (light and power from dust) in terracotta. The western end of the range and a large extension to the east were both added later, in a slightly darker variety of the pink brindled brick that was used in the original building and with lees ornamentation.
Access to the ground floor was not possible on our visit. The first floor consisted of a series of rooms leading through each other, all with decorative cornices and small fireplaces.
The second floor had a series of smaller rooms leading off a corridor running along the north side of the building. These rooms also had cornices and fireplaces and several had signs of cupboards and shelving around the walls.
The easternmost room was larger than the others. A small office adjacent had a private lavatory and hand-basin. Three further lavatories indicated a sizeable office staff. None of the rooms showed signs of domestic occupation. It was thought probable that these offices were used both for administering the destructor/generator and customers' accounts.
The western extension appeared to have had operational uses. Inserted on its first floor there was a small thick-walled room with an internal window opening rather like that of a gun embrasure. This may have been a shelter for staff on essential duties. Above was a room once divided by modern glazed partitions with a lantern roof. In it was a walk-in safe with steel shelving. A two-storeyed room at ground floor/basement contained a modern transformer and switch gear and cable racks running to a subway beneath the street. It appeared that a gallery at ground level had been removed.
DESTRUCTOR HALL
The Destructor Hall had been gutted of equipment and divided as a Highways Department store. The tall chimney had been demolished. It was a very large building, 60ft high to the apex of the roof. The windowless north and south gable walls were substantially constructed in dull-red engineering brick, buttressed by piers internally. Architecturally they were simple yet very impressive, composed of double-recessed blind panels, round-arched at the top, surmounted by shaped gablets.
The main roof was a three-pinned portal frame of lattice steel, rising above low, lean to aisles, clad top and sides with corrugated sheeting. The prominent pinned connections were probably for ease of design and erection — not an over zealous provision for thermal expansion. Steel pillars supporting the roof were formerly tied by the lattice girders of the tipping floor, but these had been removed and they were now encased in freestanding concrete piers. Lattice girders remained as braces longitudinally.
In the north wall, the burnt-off ends of steel beams indicated the levels of the feed-water storage tank, the tipping floor and the refuse storage bins. A girder and relieving arch at the centre of the north wall spanned the site of the twin flues. East of this were two blocked circular openings, the intakes to the demolished fan room, through which any foul air was exhausted from the destructor hall. The destructor chambers and the electric hoist had been removed without trace and the entrance for dust carts had been altered.
To the south was the granite-paved cartyard, with the site of the weighbridge at the eastern gateway. Another gateway beneath the office range probably allowed a one-way circulation system. A derelict lean-to at the rear of the offices was built of clinker concrete blocks. The adjoining three-storey house, 7 Hoxton Square, predated the destructor and probably provided living quarters for staff. No 6 Hoxton Square had been adapted for messrooms and stores.
The Destructor Hall looking north
ACKNOWLEDGEMENTS
This report results from site work and research carried out by Gerald Blaney, Bob Carr, Barrie Hearnden, Tom Ridge, Peter Skilton, Tim Smith, David Thomas, Malcolm Tucker, Ruth Verrall, Paul Verrall and Dennis Wire.
We would like to thank the London Borough of Hackney's Department of Planning and Development for arranging our visit. A fuller report is to be deposited with the Hackney Archivist at Rose Lipman Library. Photocopies will be available from GLIAS in due course — details will be given in the Newsletter.