**2.1 Wind Diesel system with compressed air storage (WDCAS)**

The proposed system, (WDCAS) combined with the Diesel engine supercharge, will increase of the rate of penetration of the wind energy (RPWE). The supercharging is a process which consists of a preliminary compression with an objective to raise the intake air density of engines to increase their specific power (power by swept volume) [23,24]. During periods of strong wind, the surplus of the wind power (when wind power penetration rate defined as quotient between the wind-generated power and the charge is greater than 1 e WPPR>1) is used to compress the air via a compressor and store it. The compressed air then serves to turbo-charge the Diesel engine with a dual advantage of increasing its power and decreasing the fuel consumption. The Diesel generator works during the periods of low wind velocity, when the wind power is not sufficient for the load.

The WDCAS has a very important commercial potential for remote areas as it is based on the use of Diesel generators already in place. It is conceived like the adaptation of the existing engines at the level of the intake system, the addition of a wind power station and an air compression and storage system. The lack of information on the economics, as well as on performances and reliability data of such systems is currently the main barrier to the acceptance of wind energy deployment in the remote areas. This project intends to answer some of these interrogations. Using information available [4,6,25], and performance analysis [23,26], we estimate that on a site with appreciable wind potential, the return on investment (ROI) for such installation is between 2 and 5 years, subject to the costs of fuel transport. For sites accessible only by helicopters the ROI can be less than a year [17]. This analysis does not take into account the raising prices of fuel, nor GHG credit which only tend to reduce the ROI [27].

#### **2.2 Possible techniques for making advantage of CAES to increase Diesel engine efficiency**

Among different techniques investigated, two of them were selected for being compatible with a simple adjustment of existing Diesel Power system without heavy investments:

#### **Technique 1: admission of the compressed air at the compressor inlet**

The indicated efficiency of a Diesel engine follows a quadratic variation function of Airto-Fuel ratio, as shown in Figure 4. The idea is therefore to use the CAES to increase the pressure at the intake of the compressor, as shown in Figure 5, mainly at high loads, when there is a lack of air. This would increase the air flow admitted by the engine and increase therefore the Air-to-Fuel ratio to bring it artificially to its optimal value witch is around 53.

#### **Technique 2: admission of the compressed air at the engine inlet**

The idea is to remove the turbocharger and connect directly the CAES to the inlet of the engine, as shown in Figure 6. The benefit would be increasing the scavenging work to make it contributing to the provided power, in addition to the ability to increase the Air-to-Fuel ratio as in the previous technique.

The proposed system, (WDCAS) combined with the Diesel engine supercharge, will increase of the rate of penetration of the wind energy (RPWE). The supercharging is a process which consists of a preliminary compression with an objective to raise the intake air density of engines to increase their specific power (power by swept volume) [23,24]. During periods of strong wind, the surplus of the wind power (when wind power penetration rate defined as quotient between the wind-generated power and the charge is greater than 1 e WPPR>1) is used to compress the air via a compressor and store it. The compressed air then serves to turbo-charge the Diesel engine with a dual advantage of increasing its power and decreasing the fuel consumption. The Diesel generator works during the periods of low

The WDCAS has a very important commercial potential for remote areas as it is based on the use of Diesel generators already in place. It is conceived like the adaptation of the existing engines at the level of the intake system, the addition of a wind power station and an air compression and storage system. The lack of information on the economics, as well as on performances and reliability data of such systems is currently the main barrier to the acceptance of wind energy deployment in the remote areas. This project intends to answer some of these interrogations. Using information available [4,6,25], and performance analysis [23,26], we estimate that on a site with appreciable wind potential, the return on investment (ROI) for such installation is between 2 and 5 years, subject to the costs of fuel transport. For sites accessible only by helicopters the ROI can be less than a year [17]. This analysis does not take into account the raising prices of fuel, nor GHG credit which only tend to reduce

**2.2 Possible techniques for making advantage of CAES to increase Diesel engine** 

**Technique 1: admission of the compressed air at the compressor inlet** 

**Technique 2: admission of the compressed air at the engine inlet** 

Among different techniques investigated, two of them were selected for being compatible with a simple adjustment of existing Diesel Power system without heavy investments:

The indicated efficiency of a Diesel engine follows a quadratic variation function of Airto-Fuel ratio, as shown in Figure 4. The idea is therefore to use the CAES to increase the pressure at the intake of the compressor, as shown in Figure 5, mainly at high loads, when there is a lack of air. This would increase the air flow admitted by the engine and increase therefore the Air-to-Fuel ratio to bring it artificially to its optimal value witch is

The idea is to remove the turbocharger and connect directly the CAES to the inlet of the engine, as shown in Figure 6. The benefit would be increasing the scavenging work to make it contributing to the provided power, in addition to the ability to increase the Air-to-Fuel

**2.1 Wind Diesel system with compressed air storage (WDCAS)** 

wind velocity, when the wind power is not sufficient for the load.

**2. Suggested concept** 

the ROI [27].

**efficiency** 

around 53.

ratio as in the previous technique.

Fig. 4. Variation of indicated efficiency with the air/fuel ratio [39]

Fig. 5. Admission of CAES at the compressor intake.

Fig. 6. Admission of CAES at the engine intake

Optimal Design of an Hybrid Wind-Diesel System with

balance equation of the turbocharger torque

balance equation of the turbocharger speed

The speed of the turbine and the compressor are equal:

**For an operation without CAES** 

balance equation of the crankshaft:

following:

compressor:

intake aire continuity

exhaust air continuity

**For an operation with CAES** 

Optimal Air-to-Fuel ratio

thermodynamic transformations.

**Technique 2** 

Compressed Air Energy Storage for Canadian Remote Areas 277

The unknown variables are *QQ N* int , , ,, *fuel comp p p* 3 4 and the equilibrium equations are the

*P P out load*

The torque supplied by the turbine must be equal to the necessary torque to drive the

*P P comp turb*

*N N comp turb*

*Q Q comp* int

*Q Q turb exh*

The unknown variables are *QQ N* int , , ,,, *fuel comp ppp* <sup>034</sup> and the equilibrium equations are

int 53 *fuel Q Q*

Main equations are issued from the mass and heat conservation as well as the ideal gas assumptions [6, 13]. The application of the first law or thermodynamics and the perfect gas law to the control volume results in the differential equation 1 [13] that drives all the

walls comb int exh fuel fuel *<sup>T</sup> ech d m u P dV dq dq h dm h dm h dm* (1)

the same as previous five equations in addition to the sixth following equation:

The power supplied by the engine must be equal to the resistant power:
