Overview[ edit ] Definitions of complexity often depend on the concept of a confidential " system " — a set of parts or elements that have relationships among them differentiated from relationships with other elements outside the relational regime.
It is possible that potentially useful systems are usually not considered simply because, not being conventionally used at present, they are unfamiliar and therefore are not known or understood well enough by potential buyers; this is where it is hoped that publications such as this may encourage some attempts to try new methods, preferably by institutions or individuals with the resources to underwrite the risks inherent in experimenting with new or unfamiliar technologies.
Cost-effectiveness and efficiency Generally, a cost-effective system needs to be technically efficient; i. In the former case, the energy resource, if it is solar energy, wind or water power is notionally cost-free, but the capital cost of the system is closely linked to the efficiency. This tends to require a system that is twice as large and therefore usually twice as expensive.
In all cases there is an ultimate technical efficiency that can be approached but never quite achieved, Fig. Pursuing the cause of better efficiency is usually worthwhile up to a point, but thereafter it brings diminishing returns as increasing complication, sophistication and cost is required to achieve small further gains in efficiency.
However it usually requires a mature technology to be at the level where further improvements in efficiency are counter-productive, and in any case, new manufacturing processes and materials or increases in recurrent costs due to inflation sometimes allow improvements to become cost-effective in the future which were not justifiable in the past.
The influence of efficiency on costs is illustrated in Fig. In the case of renewable energy systems these costs will be largely attributable to the capital cost and hence to financing the investment, while in the case of fossil fuelled devices a large proportion of the costs will relate to running and maintaining the system.
How diminishing returns eventually defeat the benefits of seeking increased efficiency beyond certain levels B. The influence of efficiency on costs ii.
Combining system components with differing efficiencies Virtually all pumping system components achieve an optimum efficiency at a certain speed of operation.
Some components like pipes and transmission systems are most efficient in terms of minimizing friction and hence losses at very low rates of throughput, but they are then least productive and they will therefore have a point of "optimum cost-effectiveness" where there is a good compromise between their productivity and their efficiency.
Prime movers invariably have an optimum speed of operation; this is as true of humans and animals as it is of diesel engines or windmills. It must be remembered that the efficiency of a combination of two components is numerically the product i.
Here prime mover 'A' is less efficient than 'B' but has a better speed match to the pump — hence the less efficient prime mover 'A' provides a more efficient system The important point contrived in Fig.
This illustrates how it is generally more important to ensure that the design speeds of components match properly than to ensure that each component has the highest possible peak efficiency. In such situations it generally pays, and it is sometimes essential, to introduce a speed changing transmission.
Also, in many situations the prime-mover cannot readily be close to the pump, and some method is therefore necessary for transmitting its output either horizontally or vertically to the water lifting device.
Transmission principles Power can be transmitted from a prime mover to a pump in a number of ways; the most common is a mechanical connection, which can either rotate shafts, belts or gears or reciprocate pump rods or levers.
Where power has to be transmitted some distance, then electricity, hydraulic pressure or compressed air can be used, since it is difficult to transmit mechanical power any distance, especially if changes of direction or bends are needed. In all transmissions there is a trade-off between the force or torque being transmitted by the system which demands robustness to resist it and the speed of operation which tends to cause wear and reduced life.
Power, which is what is being transmitted, can be defined as the product of force and velocity. Mechanical systems that run at slow rotational or reciprocating speeds need larger forces to transmit a given amount of power, which in turn require large gear teeth, large belts or large pump rods for example and these inevitably cost more than smaller equivalents.
Where mechanical power is transmitted some distance any reciprocating linkages need to be securely anchored; even a 5m farm windpump can pull with a reciprocating force peaking at about 1 tonne.
For this reason, most modern commercial systems involving lengthy mechanical links tend to use high speed drive shafts for example surface mounted electric motors driving a rotodynamic pump located below the water or below flood level as in Figs.
A high speed drive shaft can be quite small in section because its high speed results in low torque. However a high speed drive needs to be built with some precision and to have good and expensive bearings to carry it and to align it accurately so as to prevent vibrations, whirling of the shaft, premature wear and other such problems.
High voltage cable or high pressure pipesneed to be of a good quality and inevitably cost more per metre for a given cross section. Therefore, with all transmissions there is a trade-off between efficiency and cost; cheap transmissions often reduce the capital costs but result in high recurrent costs due to their lower efficiency and greater maintenance and replacement needs, and vice-versa.
Generally such prime-movers are used with centrifugal or other rotodynamic pumps which run at the same speed as the engine or motor; in such situations they can be direct-coupled with a simple flexible drive coupling as in Figs. Speed changing of up to about 4: In this situation the total speed change is the product of the ratios for each stage.
Where multiple vee belts are needed on one drive stage, as in Fig. Flat belts made of leather used to be common and they are coming back, sometimes today made of synthetic materials, as they are more efficient with less friction than a set of vee belts.
To be successful twisted belt drives need to have a generous distance between the pulleys in relation to their diameters or excessive wear will occur. The pump rod is connected to the cross-head or pitman.
Mechanisms of this kind can be used to connect a diesel engine or an electric motor to a reciprocating piston pump. Other mechanical right-angle drives are illustrated by reference to Figs.
The high cost is due to the mechanical requirements for reliable operation being demanding and the volume of production usually being much lower than for engines or electric motors.In a series of three articles Andrew Lambert and Andy Newall lay out their blueprint for the future of HR.
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