Water Powered Clock

History

Water clocks are among the most ancient timekeeping devices. They were used by both the Ancient Egyptians and Greeks. The Greeks gave the water clock the name "clepsydra," or "water thief." Water drains from a vessel at a fixed rate of speed. The vessel is marked to show the hours of the day. As the vessel empties, the time is shown by the level of the water. Water powered clocks use gravity as their sole source of energy.

How does it work?

 

Water-powered clocks employ an internal mechanism that extracts ions from liquid. These extracted electron molecules then create an electrical current that generates power to the device. Water-powered devices convert ions to create clean energy. This is different from H2O batteries, which are an actual battery that relies on a chemical reaction when introduced to water to create energy. Water-powered clocks and other water-powered devices do not rely on outlet-based electricity or batteries to run, making them a greener choice when choosing a household item. Water is readily in supply to keep these items up and running.

Photovoltaic systems contracting

This is an interesting experience of installing photovoltaic systems in France

 

 

photovoltaic systems - in Provence - South east of France -

The context:

The market for renewable energy and particularly the photovoltaic market has seen a very strong growth for several years in France. This sector has increased by 40% between 2007 and 2008 and 85% of the French people believe that the development of renewable energies must be a priority for the government.
The government has also responded to this expectation in 2006-2007 by implementing

• a series of taxes: including 50% tax credit …
• economics actions such as setting the purchase cost of Electricity by EdF at 0.55 € / kWh.
• in 2008 “Le Grenelle de l’Environment” a major forum in order to boost all type of actions on a State level.

Coming from the European Council, there is of course also the 2020 target of pushing to 20% the share of renewable energies in total energy consumption in European countries.
France hopes to catch up compared to other European countries, and all particularly the PACA region (Provence Alpes Côte d’Azur, south east of France), which is deficient in electricity generation. This explains why the PACA Regional Council supports  all local initiatives through its AGIR program.
The French people are now ready to commit to the environment. A poll conducted by Ipsos December 2007, on behalf of Interclima and Le Moniteur, shows that 79% of them are willing to invest in this area (Interclima + elec – News – 05/02/2008).
In this context, the last obstacle to a commitment by individuals and local communities, for the realization of photovoltaic systems is the high cost of equipment and a payback on investment too long. The objective of this interesting contracting experience is precisely to offer a 30% lower than the competition and thereby achieve a payback on investment of less than five years.
This contracting company strategy is based on 3 strong axes:

• work on costs by bundle orders
• reduced margin on photovoltaic systems and electrical equipment
• share installation work between our clients & us. (solidarity economy)

Faults in Electrical Systems

Introduction

We all are familiar and encountered at least once the phenomenon of fault occurrence in electrical system. A power system failure across the town that happened due to a storm breakout or an internal equipment fault that disrupted your local power supply – these are all essentially the cases of faults in electrical systems.
Through this article let us try to examine this phenomenon in little more detail.

What is an Electrical Fault?

An Electrical System fault can be defined as a condition in the electrical system that causes failure of the electrical equipment in the circuit such as: Generators, Transformers, Busbars, Cables and all other equipments in the system that operate at given voltage level.

Principal Fault Types

By nature of electrical systems, at the basic level, electrical faults can be categorized as:

1. Short-Circuit Faults: This is caused when there is a failure of insulation causing a short-circuit condition. This is by far the most common cause of failure.


2. Open Circuit Faults: This fault occurs when a failure happens in the conduction path of electricity

Besides this, there could be combination (Simultaneous) fault situations as well and equipment level winding faults. We will not look in to them in detail over here.
Since Short-Circuit Faults are the most common causes of faults in Electrical distribution systems, let us study them in detail:

Short-circuit Faults

A short circuit fault occurs when there is an insulation failure between phase conductors or between phase conductor(s) and earth or both. An insulation failure results into formation of a short-circuit path that triggers a short-circuit conditions in the circuit (i.e. abnormally high current situations followed by visible effects like arcing, flashing).
Figure 1.0 below depicts a three phase-to-earth balanced fault condition:

Fig 1.0: Three Phase-to-Earth Balanced Fault Condition

Two other most common unbalanced fault conditions seen in a balanced three phase electrical system are:

• Phase-to-Phase fault: In this, only two of the three phases get short-circuited, causing an unbalanced fault condition in the system. Figure 2.0 below depicts this fault condition.

Fig 2.0: Phase-to-Phase unbalanced Fault Condition

• Single phase-to-earth fault: In this, one of the three phases get short-circuited with ground, causing an unbalanced fault condition in the system. Figure 3.0 below depicts this fault condition.

Fig 3.0: Single Phase-to-Earth unbalanced Fault Condition

Normally during operations, the fault situations may be dynamic and change the fault types rapidly based on local conditions. (e.g. a single phase-to-earth fault may in turn change to a two phase-to-earth fault)

Conclusion

A fault’s severity and magnitude depends on variety of factors like the location of fault in the electrical system, damage caused due to fault. While analyzing a given fault’s severity, it is a usual practice to refer to a standard fault condition (three phase fault) for given voltage level.
A three phase fault is considered as the most severe fault that can occur in the system and hence its short-circuit ratings are used while determining the required switchgear system. Besides this, a single phase-to-earth fault current ratings are also considered in short-circuit calculations.

The Full Wave Rectifier

In the previous Power Diodes tutorial we discussed ways of reducing the ripple or voltage variations on a direct DC voltage by connecting capacitors across the load resistance. While this method may be suitable for low power applications it is unsuitable to applications which need a “steady and smooth” DC supply voltage. One method to improve on this is to use every half-cycle of the input voltage instead of every other half-cycle. The circuit which allows us to do this is called a Full Wave Rectifier. Like the half wave circuit, a Full Wave Rectifier Circuit produces an output voltage or current which is purely DC or has some specified DC component. Full wave rectifiers have some fundamental advantages over their half wave rectifier counterparts. The average (DC) output voltage is higher than for half wave, the output of the full wave rectifier has much less ripple than that of the half wave rectifier producing a smoother output waveform. In a Full Wave Rectifier circuit two diodes are now used, one for each half of the cycle. A multiple winding transformer is used whose secondary winding is split equally into two halves with a common centre tapped connection, (C). This configuration results in each diode conducting in turn when its anode terminal is positive with respect to the transformer centre point C producing an output during both half-cycles, twice that for the half wave rectifier so it is 100% efficient as shown below. Full Wave Rectifier Circuit: