Monday, 27 July 2009

Span of control

From my experience, an optimal span of control is seven sub-ordinates. At lower levels of the organization,
however, where there is less interlocking, or where responsibility is concerned more with the performance of specific tasks, the span of control may be larger. It varies widely in different organizations from three to twenty.

A number factors influence the limit of span of control and these include:
- Technology (Cell phones, email, and other forms of technology that facilitate communication and the exchange of information make it possible for managers to increase their spans of management over managers who do not have access to or who are unable to use the technology)
- organization level
- job complexity (Subordinate jobs that are complex, ambiguous, dynamic or otherwise complicated will likely require more management involvement and a narrower span of management).
- job similarity (The more similar and routine the tasks that subordinates are performing, the easier it is for a manager to supervise employees and the wider the span of management that will likely be effective.)
- supervisory specialities
- measure of overall organization effectiveness
- the nature of the organisation
- the ability and personal qualities of the manager including the capacity to cope with interruptions (Some managers are better organized, better at explaining things to subordinates, and more efficient in performing their jobs. Such managers can function effectively with a wider span of management than a less skilled manager)
- the amount of time the manager has available from other activities to spend with subordinates
- the ability and training of subordinate staff (Managers who supervise employees that lack ability, motivation, or confidence will have to spend more time with each employee. The result will be that the manager cannot supervise as many employees and would be most effective with a narrower span of management)
- the effectiveness of co-ordination and the nature of communication and control systems
- the physical location or geographical spread of subordinates (The more geographically dispersed a group of subordinates the more difficult it is for a manager to be in regular contact with them and the fewer employees a manager could reasonably oversee, resulting in a narrower span of management)
- the length of the scalar chain

If the span of control is too wide, it becomes difficult to supervise subordinates effectively and this places stress on the manager. With larger groupings, informal leaders and sub-groups or cliques are more likely to develop, and these may operate contrary to the policy of management. There may be lack of time to carry out all activities properly. Planning and development, training, inspection and control may suffer in particular, leading to poor job performance. A wide span of control may limit opportunities for promotion. Too wide a span of control may also result in a slowness to adapt to change or to the introduction of new methods or procedures.

If the span of control is too narrow, this may present a problem of co-ordination and consistency in decision-making, and hinder effective communications across the organisation structure. Morale and initiative of subordinates may suffer as a result of too close a level of supervision. Narrow spans of control increase administrative costs and can prevent the best use being made of the limited resource of managerial talent. They can lead to additional levels of authority in the organisation creating an unnecessarily long scalar chain.

Downsizing, in which firms attempt to cut costs by eliminating positions, has become popular among major corporations in recent years. This strategy has had an impact on decentralization and span of control. Employees who used to report to managers whose positions were eliminated have been assigned additional responsibilities. Span of control has become wider in downsized companies, and workers have become less specialized as they have taken on additional duties.

Wednesday, 22 July 2009

Renewable energy growth

Annual renewable energy investment has increased from $63 billion in 2006 to $104 billion in 2007 and $120 billion in 2008. In the four years from end-2004 to end-2008, solar photovoltaic (PV) capacity increased sixfold to more than 16 gigawatts (GW), wind power capacity increased 250 percent to 121 GW, and total power capacity from new renewables increased 75 percent to 280 GW, including significant gains in small hydro, geothermal, and biomass power generation. During the same period, solar heating capacity doubled to 145 gigawatts-thermal (GWth), while biodiesel production increased sixfold to 12 billion litres per year and ethanol production doubled to 67 billion litres per year.

Annual percentage gains for 2008 were even more dramatic and wind power grew by 29 percent and grid-tied solar PV by 70 percent. The capacity of utility-scale solar PV plants (larger than 200 kilowatts) tripled during 2008, to 3 GW. Solar hot water grew by 15 percent, and annual ethanol and biodiesel production both grew by 34 percent. Heat and power from biomass and geothermal sources continued to grow, and small hydro increased by about 8 percent.

During 2008, the United States became the leader in new capacity investment with $24 billion invested, or 20 percent of global total investment. The United States also led in added and total wind power capacity, surpassing long-time wind power leader Germany. Spain added 2.6 GW of solar PV, representing a full half of global grid-tied installations and a fivefold increase over Spain’s 2007 additions. China doubled its wind power capacity for the fifth year in a row, moving into fourth place worldwide. Another significant milestone was that for the first time, both the United States and the European Union added more power capacity from renewables than from conventional sources (including gas, coal, oil, and nuclear).

It’s impossible to separate the ‘technical’ and ‘financial’ aspects of the subject of renewable energy from the ‘politics’ which surround it. This is because the technical/financial/political aspects are intertwined; an available energy supply is the cornerstone of any economy and politicians are extremely interested in how economies perform. Politicians like short-term solutions and are reluctant to introduce measures which will make them unpopular.

Power generation using fossil fuels creates many economic externalities that are not taxed or banned by governments to control their use. For example, coal-fired power generation creates the negative externalities of emissions of mercury, NOx, SOx and COx. Many governments don’t limit these negative externalities, created by the power producers, for fear of impact upon the cost of electricity. Consequently, power generation using fossil fuels will always cost less than renewable energy until governments protect their citizens and the planet from the adverse effects of the emissions of mercury, NOx, SOx and COx.

Obviously, people do prefer renewable technologies. It is up to governments to use legislation and fiscal measures to create a level playing field where renewable energy cleanliness is rewarded and fossil fuel negative externalities like emissions of mercury, NOx, SOx and COx are penalized at the correct scale. By this method, renewable energy costs from sources like; solar, wind, tidal and hydro would be equal to those costs achieved with ‘clean’ fossil fuel power generation.

Tuesday, 21 July 2009

Wind power production

The success of wind power production depends on wind speed and the actual energy of the wind varies with a multiple power of the wind speed. Double the wind speed, and the wind energy increases more than eightfold.

A 2 kW wind turbine at a site with a wind speed of 12 mph may generate around 1300 kWh/year for a constant wind location, i.e. 150 watts for 8760 hours. At a wind speed of 19 mph, the output could rise to 6000 kWh/year and, at 23 mph, the annual output could be 15,000 kWh. Other factors limit turbine output at very high wind speeds. However, these figures show that good site selection is important for wind power project economics. If the wind only blows for part of the day or week then the number of kWh per year are reduced.

A windy site is starting point for any wind turbine project, but there are other factors too. Wind speed varies with height; the higher a turbine is raised above the ground, the better the wind regime. This benefits larger wind turbines that are placed on higher towers, but larger turbines tend to be more efficient anyway, so additional advantages accrue.

Depending on the efficiency of a wind turbine, there is a cut-off wind speed below which wind power generation is not considered economical. This figure depends on the efficiency of wind turbine design as well as on the turbine cost. With the turbines available at the moment, a wind speed as low as 10 mph is considered economically exploitable at an onshore site. Since offshore costs are higher, an offshore wind speed of 15 mph is needed to make a site economically attractive.

Once a potential site has been identified, it must be studied in more detail to confirm that it is suitable. Long- and short-term wind speed measurements will normally be needed to ascertain the wind regime. Figures for at least one full year will normally be required, longer if possible.

When wind passes over land, the unevenness of the ground and interference to wind flow from trees or undergrowth cause a significant amount of turbulence. Turbulent air creates an additional strain on a wind turbine blade, accelerating the onset of fatigue damage. In order to limit this damage as much as possible, wind turbines are normally placed on a tower, which is tall enough to raise the blades above this turbulent layer of air.

Most wind turbines have blades attached perpendicularly to a horizontal shaft and this arrangement imposes restrictions on the wind turbine design because the turbine must be raised on a tower for the blades to clear the ground and the turbulent layer of air next to it. Additionally, a yawing system is needed so that the rotor and generator enclosure can be rotated as the wind direction changes.

Alternatively, a vertical axis machine has all its weight supported by a ground-level bearing. However, the vertical configuration has not yet achieved significant commercial success.