The White Cliffs Solar Steam Engine


The following is an excerpt from a report entitled "The White Cliffs Project - Overview for the period 1979-89" published by the Department of Energy of the government of New South Wales in 1991. Pages 85-90 have been reproduced with the permission of the NSW DOE.

For more information on this report and where to order a copy, click here. The NSW DOE has an on-line order-form and a list of its publications here.

GOOD NEWS!After having received dozens of requests over the years for a full version of this report, the NSW government has finally scanned it and published it online! And just in case they decide to reorganise again, here is my local copy.


3.4 The Steam Engine

In recent years much effort has been directed to developing, on the one hand, high efficiency heat engines (for example employing Stirling, Brayton and other cycles) for utilizing, very efficiently, the high quality heat from concentrating solar collectors; and on the other, to produce very inexpensive low efficiency steam and other engines which can be built in Third World workshops and supplied by energy from biomass. The former objectives have not as yet been realised because problems of performance, especially reliability and cost effectiveness, have not been adequately overcome; the latter also for various reasons have not resulted in that technology reaching significance.

But there is another approach, relevant to these application areas, which employs medium level technology and is based on mass-produced readily-available components, supplemented by some special items to produce steam engines with heat-to-mechanical work conversion efficiencies of over 20%, robust, reliable, able to be maintained by those with automotive and agricultural experience, and having the potential for cost-effectiveness for many applications.

Such engines have resulted from our development of the White Cliffs Solar Thermal Power Station [Kaneff 1983, 1987], where a unit has operated for many thousands of hours giving electricity supply reliably. Other units are currently working in the USA (in Troy NY, at Albuquerque NM and at the Sandia test facility, preparatory to operation on Molokai Hawaii); please see Appendix I. Further units are to be used for a rural village power supply in Fiji and for the utilisation of crop wastes in Australia. Figure 41 shows the White Cliffs engine.

3.4.1 Engine Details - Piston Operated Valves (POV)

For reasons already indicated, this unit employs a diesel engine converted to steam operation. The particular unit employed a Lister 3-cylinder engine - is used in its thousands in Australia and has the advantage that each cylinder and head is removable.

Most of the engine is made from parts of two diesel engines (Lister and Ceneral Motors) which are on the market. The general form of the engine is shown in Figure 42. Steam is supplied to a chamber in the head of each cylinder; the engine is started by a standard electric motor. As a piston approaches top dead centre, the pins in its crown lift the three ball valves from their seats and steam enters the cylinder until the valves seat again past dead centre. The steam expands while applying pressure to the piston until the piston exposes the normal exhaust ports in the cylinder liner which was made for a 2-stroke diesel engine. The cylinders, cylinder heads, valve seats and steam chambers, that is, the conversion components, can be produced by relatively simple workshop techniques from cast iron, mild steel and stainless steel.

All parts of the engine are inexpensive, do not require special machine tools to fabricate, and two men could rebuild the engine with replacement parts between sunset and sunrise should that ever prove to be necessary.

Automated starting or stopping is facilitated by the 3 motor-driven valves - bypass, throttle (really an on/off valve only), and drain valve.

When the engine is stationary, a motorised bypass valve is open and water or steam from the solar collectors passes to the condenser until the steam conditions are correct for the engine to start. As water can collect in the steam line to the engine, on start when the throttle opens, water and steam arrive at the engine. With water in the cylinders, the starter motor cannot crank the engine if the water can escape only via the inlet valves. Consequently, a motor-operated drain valve is fitted with a port to each cylinder. Interlocks prevent the starter functioning until the drain valve is open. In configurations which do not allow water buildup in lines, this drain valve is not necessary. When it is the water can flow to the evacuated exhaust line to the condenser, through ports which limit the amount of steam lost. As soon as the engine starts the drain valve is closed by a signal from a speed measuring instrument. When the engine is running, any water in the steam from the solar collectors is diverted via a steam trap into exhaust lines.

Two major areas of development were necessary:

1. The Valve Mechanism

Extended reliable operation was achieved only after much attention to geometric configuration and dimensions, satisfactory valve constraints and especially achievement of a satisfactory materials and hardness matching between all appropriate components.

2. Oil-Water Treatment

The engine exhausts into an evacuated condenser via a vortex chamber which collects most of the engine lubricant and water droplets. however, the steam carries some oil droplets which must be removed before the water is recirculated through the solar collectors.

A process using little power was devised to do this and return as much as possible of the oil to the engine. This is already described in Section 3.3.10, but in more detail, the exhaust steam line enters tangentially the upper end of a cylindrical vortex chamber. Oil and water droplets are stopped by a gauze sleeve on the inner surface and drain to the bottom of the chamber; the steam passes up through stainless steel wool held in a cylinder, which is attached to the top plate of the vortex chamber. The smallest oil drops pass into the condenser with the steam and the condensate carries these as a very fine suspension to compartment 1 of the feedwater tank via the casuum [sic?] pump. This dispersion of oil in the condensate cannot be removed by conventional filters or the centrifuge, and special fine filters must be employed.

Some 2 ml/s of oil is recovered from the engine exhaust with the complete condensate treatment - the oil is washed and cleaned by this process, leaving solids in the various filters.

The White Cliffs engine configuration is:

Bore: 98.4mm
Stroke: 114.3mm
Number of Cylinders: 3
Maximum Steam Pressure: 70 kg/cm2 (abs) (6.9 MPa)
Maximum Steam Temperature: 450°
Condenser Pressure: 0.25 kg/cm2 (abs) (24.5 KPa)
Expansion Ratio (Adjustable): 1.25 (used)
Lubrication: as in Lister engine
Lubricant: specially selected
Measured Efficiency (at Steam Pressure 42 kg/cm2, Temperature 415°): 21.9%

3.4.2 Auxiliary Boiler

An auxiliary monotube boiler is available for testing the engine and to act as a backup if the diesel unit is out of service.

3.4.3 Performance

Table VII shows representative performance characteristics and Figure 43 indicates efficiency varitions at different steam temperatures for four different thermal power inputs - these measurements were made by P. Holligan and M. Williams, NSW Energy Authority, in August 1983. It is apparent that efficiency drops slowly with reduction of superheat until saturated steam results, after which operation on wet steam causes a rapid reduction in efficiency as degree of 'wetness' increases. Figure 41 shows the engine at White Cliffs; a later version is indicated in Figures 44(a) and (b); a block before conversion is shown in Figure 44(c). Engine operation is described in Section 1.1. We consider this engine technology has good potential and scope for considerable further improvement.

Tables and Figures

As usual, click on the thumbnail images for the larger versions.

Figure 42
- Engine details Figure 43
- Performance graph Table 7 -
Performance table
Figure 42 - Basic White Cliffs Engine Details showing piston-operated valves, steam chambers, exhaust ports, and engine block
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Figure 43 - White Cliffs Steam Engine Performance
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Table 7 - Steam Engine Performance
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Figure
44a - Engine without insulation Figure
44c - Engine block before conversion Figure
44b - Engine in working order
Figure 44(a) - 3 Cylinder Engine Conversion, a later development than the engine of Figure 41. Insulation has been removed to show the cylinders
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Figure 44(c) - A 3 Cylinder Engine Block before Conversion (as many of the original components as possible are used).
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Figure 44(b) - The Engine of Figure 44(a) in working order (Note Vortex Chamber to the left, and condenser above vortex chamber).
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Erik Rossen <rossen@rossen.ch>
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Copyright © 2000 until the heat-death of the Universe (thanks, Mickey!), by Erik Rossen
Last modified: 2011-05-09T09:14:34+0200

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