 |
 |
 |
|
The uncontested reason that such a system could be developed is the environmental benefits. Electricity production from renewable energy sources such as wind and solar energy have no emissions at all. From the other hand using Hydrogen and Biomass can cause same damage to the environment but in any case is much less than the pollution caused by the energy production from Fossil fuels such as coal and oil. It is accepted that the quantity of CO2, NOx and SO2 produced from the combustion of biomass is less than the one needed by the biomass plant to grow up. Also scientists have the suspicion that wide use of Fuel Cells will decrease the ozone concentration levels
If hydrogen were to replace fossil fuel entirely, it is estimated that 60 to 120 trillion grams of hydrogen would be released each year into the atmosphere, assuming a 10-20% loss rate due to leakage. This is four to eight times as much hydrogen as is currently released into the atmosphere by human activity, and would result in doubling or tripling of inputs to the atmosphere from all sources, natural or human.
Because molecular hydrogen freely moves up and mixes with stratospheric air, the result would be the creation of additional water at high altitudes and, consequently, an increased dampening of the stratosphere. This in turn would result in cooling of the lower stratosphere and disturbance of ozone chemistry, which depends on a chain of chemical reactions involving hydrochloric acid and chlorine nitrate on water ice.
The estimates of potential damage to stratospheric ozone levels are based on an atmospheric modeling program that tests the various scenarios that might result, depending on how much hydrogen ends up in the stratosphere from all sources, both natural and anthropogenic.
Ideally, a hydrogen fuel-cell vehicle has no environmental impact. As it was shown in the Fuel Cell Principles" section, energy is produced by combining hydrogen with oxygen pulled from the atmosphere, and the tailpipe emission is water. By comparison, the internal combustion engine uses fossil fuels and produces many pollutants, including soot, noxious nitrogen and sulfur gases, and the "greenhouse gas" carbon dioxide. While a hydrogen fuel-cell economy would almost certainly improve urban air quality, it has the potential unexpected consequences due to the inevitable leakage of hydrogen from cars, hydrogen production facilities, the transportation of the fuel.[1]
The emissions caused by most modes of travel and all energy sources that produce electricity and heat, are presented to the following table.
| Mode of Travel | CO2 | CO | NOx | Particulates |
|
Transportation |
||||
| Gasoline Car[3] (gr/km/vehicle) | 168 | 6.6 | 1.2 | 0.1 |
| Diesel Car[3] (gr/km/vehicle) | 142 | 0.38 | 0.77 | 0.3 |
| Hybrid Car[1] (gr/km/passenger) | 125 | n/a | 0.19 | n/a |
| Rail[1] (gr/km/passenger) | 72.5 | n/a | n/a | n/a |
| Air[1] (gr/km/passenger) | 212.5 | n/a | 0.44 | n/a |
| Taxi[1] (gr/km/passenger) | 223.13 | n/a | 1.52 | 0.41 |
| Coach/Bus[1] (gr/km/passenger) | 56.25 | n/a | 0.19 | 0.02 |
| Tube[1] (gr/km/passenger) | 106.88 | n/a | 0.08 | n/a |
| Fuel Cell Car (gr/km/vehicle) | 0 | 0 | 0 | 0 |
| Energy Source | CO2 | SO2 | NOx | Particulates |
|
Electricity Generation (Kg/TJ) |
||||
| Coal (FGD & Low NOx burners)[2] | 247,000 | 320 | 725 | 45 |
| Gas - CCGT[2] | 236 | 0 | 3 | 0 |
| Oil Plant[2] | 204 | 3,750 | 1003 | 108 |
| Diesel[2] | 191,000 | 301 | 3,279 | 30 |
| Wind[2] | 0 | 0 | 0 | 0 |
| Photovoltaics[2] | 0 | 0 | 0 | 0 |
| Solar Thermal[2] | 0 | 0 | 0 | 0 |
| Biomass Gasification[2] | 4,000 | 13 | 118 | 10 |
| Biomass Steam Cycle[2] | 6,000 | 23.5 | 497 | 238 |
| Waste Compustion[2] | 100,000 | 697 | 843 | 73 |
| Biodiesel[2] | 0 | 140.4 | 150.3 | 21.2 |
| Bioethanol[2] | 0 | 148 | 170.4 | 16.1 |
| Biogas AD[2] | 3,000 | 100 | 220 | 8 |
| Biogas Landfill[2] | 0 | 83 | 580 | 28 |
| Geothermal[2] | 0-20,000 | 0 | 0 | 0 |
| Small Hydro[2] | 0 | 0 | 0 | 0 |
| Wave[2] | 0 | 0 | 0 | 0 |
| Tidal[2] | 0 | 0 | 0 | 0 |
| Fuel Cells[2] | 0 | 0 | 0 | 0 |
|
Heating (Kg/TJ) |
||||
| Solar Thermal[2] | 0 | 0 | 0 | 0 |
| Biomass[2] | 2,000 | 5.3-7.8 | 38.4-166 | 2.5-79.3 |
| Geothermal [2] | 2,000 | 0 | 0 | 0 |
| Industrial coal boiler[2] | 110,000 | 1396 | 236 | 208 |
| Solar Thermal Heat[2] | 65 | 0 | 126 | 0 |
|
[1]Tyndall Centre for Climate Change Research [3]Lipasto |
||||
Considering the data given in the above table, the emissions saved from the proposed hypothetical scenario were estimated. The values of the basic gas pollutants such as CO2, C, NOx and SO2 were calculated in the sectors of transportations, electricity generation and heating production for the year 2002 and are presented in the following table.
The total kilometers driven for the year 2002 in Crete were 1.888∙109 Km and in Karpathos and Kasos 4.379∙106 Km. Multiplying these values with the emissions (in gr/kilometer) shown in the above table (168gr CO2, 6.6gr CO, 1.2gr NOx and 0.1gr Particulates) the emission savings were calculated and are shown in Table 1.
Additionally when diesel plants were used to generate electricity, for each TJ of electricity were produced 191,000 kg CO2, 301kg SO2, 3,279 kg NOx and 30 kg of participants. Calculations were done using the formula:
[emission savings] = [emission savings in kg/TJ] ∙ [energy produced in TJ]
So in the case of Crete where 6,904 TJ of electricity were generated there were produced 1,318,740 ton of CO2, 2,0780 ton SO2, 22,639 tn NOx and 207 tn of particulates. Similarly for the case study of Karpathos and Kassos the emissions saved from the use of diesel generators were calculated and the results are shown in Table 1.
The annual electricity demand in Crete is 1.92 TWh and was considered to be covered by the Biomass Gasification Plants, hence the emissions caused to the biomass plants were taken into consideration and were subtracted from the emissions produced from the diesel generators. The results are shown in Table 1. The emissions produced by the Biomass plants were 27,600 tn CO2, 76,000 tn SO2, 1,025 tn NOx and 69 tn of participants.
In the case of Crete the Biomass Plants were co generating electricity and heating. Thus, in this case the emission savings were calculated to be as those of an industrial coal boiler and are presented in Table 1.
|
Emissions savings (tn/2002) - Table 1 |
|||
| Crete | Karpathos and Kasos | ||
|
Emission |
Transportation | ||
|
Hydrogen Plant & Fuel Cells |
CO2 | 317,400 | 735 |
| CO | 12.466 | 29 | |
| NOx | 2.266 | 5.2 | |
| Particulates | 37 | 0.08 | |
| Heating | |||
| Biomass Plant | CO2 | 1,076,000 | - |
| SO2 | 2,600 | - | |
| NOx | 1,075 | - | |
| Particulates | 179 | - | |
| Electricity | |||
|
Biomass Plants & Wind Farms |
CO2 | 1,291,000 | 16,370 |
| SO2 | 2,000 | 25.4 | |
| NOx | 21,610 | 274 | |
| Particulates | 138 | 1.750 | |
| TOTAL | CO2 | 2,684,700 | 17,100 |
| CO | 12,466 | 29 | |
| SO2 | 4,600 | 25.4 | |
| NOx | 24,950 | 276 | |
| Particulates | 355 | 1.85 | |
The undisputable conclusion is that the environmental benefits of such a system are quite important and lead to a sustainable way of covering the energy demands.