5. Results

Thigh � Tlow

<sup>Σ</sup> ð Þ kWh=hr <sup>=</sup>Efficiency � <sup>ð</sup>3412 Btu=kWhÞ � 1 ft3

measured in industry standard cubic feet (ft<sup>3</sup>

Micro-Grids - Applications, Operation, Control and Protection

converted to cubic feet of gas (Eq. 4):

Annual climate control needs for cities of interest.

4.3.2 Estimated usage

Table 6.

water, 17.0% [58].

10

The annual volume of natural gas (NG) required to run the cogeneration system,

=103:7 BTU (4)

Building performance in terms of ENERGY STAR rating (EGR) was not modified.

Usage was normalized to environmental conditions in each of the given cities as follows. Daily average high and low temperatures for obtained for each city [57]. Hourly temperatures were calculated using a linear regression each day of the year in each city, starting from the daily low for the day at 1:00 a.m. up to the daily high for the day at 12:00 noon and going back to the daily low again at 12:00 midnight. It was assumed that, on any given day, air conditioning (AC) would be required at or above a daily high of 80°F, and heat would be needed at a daily low of 50°F (Table 6).

In order to estimate the base electric usage for the proposed development, the hourly base building usage data provided by GridMarket was increased by 30% for each day for each city that air conditioning was assumed to be needed. (Given that the New York City data is actual usage, days that the data indicated that air conditioning would be needed in both New York and any other given city were not modified.) This provided a reference point for the estimated electrical load for the proposed development being connected to the regional/national power grid. Since inclusion of the microgrid would essentially eliminate electricity usage for air conditioning, daily usage data for the development with an included microgrid was reduced by 30%

Days Cairo Lagos Shanghai Mumbai London Mexico City NYC Sao Paolo AC 206 365 103 365 0 110 98 245 Heat 63 0 107 0 199 107 178 0 None 96 0 155 0 166 148 89 120

Hourly heat usage for both hot water and building heat was assumed to remain constant across all cites and climates since the heat capacity of water is constant and the amount of hot water required on a daily basis would be independent of location or climate. Also, as the configuration (and hence the volume) of the buildings was identical in all cities, and the need for heating is temperature dependent, the amount of heat required to provide building heat on an hourly basis would also be constant. Hourly heat requirements for both needs were therefore calculated based upon the New York City data and applied to all cities. The total annual energy use breakdown for New York is available from the United States Energy Information Agency as follows: electricity, 27.2%; heating, 55.8%; and hot

Total actual electrical usage for the four-tower development was converted to

assuming that air conditioning increases daily load by 30% (Table 6).

BTUs and divided by 0.272 (27.2%) to give total energy usage (Eq. 5):

hourly energy input, (kWh/hr) divided by hourly efficiency of cogeneration and

 <sup>=</sup>Thigh <sup>¼</sup> <sup>0</sup>:<sup>61</sup> (2) BTU=hour gross ð Þ� 0:61 (3)

), was calculated by summing the

#### 5.1 Infrastructure impact

Infrastructure impact is defined by the degree that the implementation of an integrated development model would relieve strain on the local power distribution grid. As can be seen in Table 7, this is highly correlated to air-conditioning needs as shown in Table 6. This is the expected result as heat provided from the trigeneration plant to the absorption chillers replaces electrical load for air conditioning. Mumbai and Lagos, cities which essentially require air conditioning yearround, had the highest reduction in load, while London, which essentially requires no air conditioning, saw no reduction in load.

The microgrid must be grid-connected for both safety and regulatory reasons in an urban environment. To be effective, the system must not add additional load to the grid but must also be balanced in order to protect the local grid infrastructure; it should not push power onto the distribution grid at any point. In case of emergency, such as a blackout condition, the microgrid should also be able to disconnect from the local power grid and provide all needed services in island mode. Table 7 indicates that the proposed model succeeds in this respect. The incorporated power generating systems produce surplus electricity on an hourly basis between 40% and 60% of the time, depending upon the city ("% hours off-grid"). Excess energy produced in hours of low load can be stored in incorporated batteries to meet demand in hours of high load, producing a system that is completely grid-neutral throughout the year. The annual difference between electricity usage and


#### Table 7.

Load and production comparison (selected cities).

production in each city as shown in Table 7, be it positive or negative, is small and can be corrected in the local design phase.

sums of all rentals in Table 10 to determine the number of years to repay the development if built conventionally and the "Cost-With Microgrid" divided by the sum of all rentals plus electricity revenue in Table 10 used. Operating and real estate costs were not considered in the gross time to repay, but it can be assumed

Construction cost comparison of proposed development: incorporating vs. not incorporating a microgrid.

From Table 11, it can be seen that the gross time to repay initial investment is lower when the microgrid is present. This has positive sociological implications. Since repayment time is shorter, long-term revenue will be higher, making the proposed development model economically profitable and therefore feasible. This has an additional advantage; the charging of premium rents is not economically required due to the lower repayment time of a microgrid inclusive development. The enhanced revenue stream and lowered operating costs associated with building a development around this model would also make affordable housing economically viable, serving to include those who are often left behind and displaced when a

Buildings generate greenhouse gases indirectly by consuming electricity produced from various fuels and directly generate such gases through the production of heat and hot water. Table 12 presents the breakdown of fuels used to generate electricity for the local power grid in each of the cities of interest [67]. Table 13 shows the greenhouse gas emissions for each of those sources per kWh [68]. Table 14 presents the percentage of energy derived from renewable sources incorporated into the microgrid in each city of interest. Table 15 contains data on natural gas usage for the development both with and without inclusion of the microgrid. In both cases, annual hot water needs are calculated according to Eq. 7 multiplied by 8760 hr/year, and heating needs are calculated by Eq. 8 multiplied by the number of heating hours estimated in each city from Table 6. For the traditional version of the development, it is assumed that these needs will be supplied by burning natural gas, although less environmentally friendly fuel oil could also be used. When the microgrid is present, heat and hot water needs are met first by trigeneration waste heat, and any unmet needs are met by the same natural gas feed that would fuel the gas turbines. Finally, Table 16 compares the calculated greenhouse gas emissions

that these costs will be identical in both scenarios in any given city.

between the two scenarios with data from Tables 8, 13, 14 and 15.

neighborhood is redeveloped.

City Res.

Mexico City

Sao Paolo

Table 9.

twrs

Com. tws

DOI: http://dx.doi.org/10.5772/intechopen.83560

Total sq. ft.

Microgrids: Applications, Solutions, Case Studies, and Demonstrations

Per sq. ft. res.

Cairo 3 1 5,504,607 \$31.13 \$35.94 \$184,295,560 \$203,898,620 Lagos 3 1 5,504,607 \$30.00 \$32.00 \$170,517,480 \$190,120,540 Shanghai 3 1 5,504,607 \$21.23 \$33.82 \$150,725,311 \$170,328,371 Mumbai 3 1 5,504,607 \$18.96 \$20.09 \$107,406,636 \$127,009,696 London 3 1 5,504,607 \$112.63 \$120.56 \$641,312,692 \$660,915,752

NYC 3 1 5,504,607 \$285.32 \$534.00 \$2,239,432,901 \$2,259,035,961

Per sq. ft. com.

3 1 5,504,607 \$52.41 \$22.36 \$207,672,921 \$227,275,981

3 1 5,504,607 \$18.11 \$42.17 \$164,401,051 \$184,004,111

Cost-less microgrid Cost-with microgrid

5.3 Environmental impact

13

#### 5.2 Socioeconomic impact

The cost of constructing the proposed development buildings was calculated using local average construction cost data and applying it to the total square footage found in Table 5 (Table 9-"Cost-Less Microgrid") [61]. The cost of integrating the microgrid is calculated on average prices in the United States (Table 8) [62]. An internally consistent data set containing all cities of interest for this metric was not found. It is assumed that the cost would be fixed since the capital components required are not locally produced. The cost of batteries, absorption chillers, and heat exchangers was not included, as it is assumed that these costs would be balanced by the deletion of HVAC equipment, cooling towers, boilers, and hot water heaters. Cost differential is presented in Table 9.

Revenue is calculated on local monthly rental rates per square foot of rental. As previously mentioned, rentable space is calculated at 50% of available floor space. Internally consistent residential rental rates were found [63]. However, internally consistent rates for residential, commercial, and retail were only found for New York City [64, 65]. Therefore, commercial rates for other cities are calculated at the ratio of those rates to residential rates for New York. As the microgrid will also be a revenue source, local electricity rates are included and applied to the revenue for each city [66]. Total annual revenue from rents and electrical for each city, as well as the rates used, is given in Table 10. Table 11 then estimates the gross time to repay the initial investment, with "Cost-Less Microgrid" in Table 9 divided by the


Table 8. Microgrid cost.


Microgrids: Applications, Solutions, Case Studies, and Demonstrations DOI: http://dx.doi.org/10.5772/intechopen.83560

Table 9.

production in each city as shown in Table 7, be it positive or negative, is small and

NYC 1.81E+08 1.63E+08 10.0% 1.71E+08 55.8% 8,533,701 5%

Saved Microgrid

Cairo 1.96E+08 1.75E+08 10.6% 1.73E+08 48.0% (2,274,872) 1% Lagos 2.05E+08 1.60E+08 21.8% 1.75E+08 61.8% 14,415,926 9% Shanghai 1.83E+08 1.80E+08 1.2% 1.76E+08 44.0% (4,663,087) 3% Mumbai 2.16E+08 1.69E+08 21.6% 1.77E+08 57.7% 8,210,049 5% London 1.81E+08 1.81E+08 0.0% 1.72E+08 41.2% (9,295,666) 5%

production (kWh/year)

1.90E+08 1.77E+08 7.0% 1.73E+08 48.3% (3,766,257) 2%

2.12E+08 1.71E+08 19.6% 1.76E+08 51.8% 5,855,500 3%

Hours offgrid

Surplus/ deficit (kWh/year) Surplus/ deficit

The cost of constructing the proposed development buildings was calculated using local average construction cost data and applying it to the total square footage found in Table 5 (Table 9-"Cost-Less Microgrid") [61]. The cost of integrating the microgrid is calculated on average prices in the United States (Table 8) [62]. An internally consistent data set containing all cities of interest for this metric was not found. It is assumed that the cost would be fixed since the capital components required are not locally produced. The cost of batteries, absorption chillers, and heat exchangers was not included, as it is assumed that these costs would be balanced by the deletion of HVAC equipment, cooling towers, boilers, and hot water heaters.

Revenue is calculated on local monthly rental rates per square foot of rental. As previously mentioned, rentable space is calculated at 50% of available floor space. Internally consistent residential rental rates were found [63]. However, internally consistent rates for residential, commercial, and retail were only found for New York City [64, 65]. Therefore, commercial rates for other cities are calculated at the ratio of those rates to residential rates for New York. As the microgrid will also be a revenue source, local electricity rates are included and applied to the revenue for each city [66]. Total annual revenue from rents and electrical for each city, as well as the rates used, is given in Table 10. Table 11 then estimates the gross time to repay the initial investment, with "Cost-Less Microgrid" in Table 9 divided by the

Cogeneration \$895 Per kW 15,660 MW \$14,015,700 Solar panels \$2434 Per kW 2100 Watts \$5,111,400 Wind turbines \$1630 Per kW 292 Turbines \$475,960

Total \$19,603,060

can be corrected in the local design phase.

Load and production comparison (selected cities).

Cost differential is presented in Table 9.

5.2 Socioeconomic impact

City No

Mexico City

Sao Paolo

Table 7.

Table 8. Microgrid cost.

12

microgrid (kWh/year)

Microgrid (kWh/year)

Micro-Grids - Applications, Operation, Control and Protection

Construction cost comparison of proposed development: incorporating vs. not incorporating a microgrid.

sums of all rentals in Table 10 to determine the number of years to repay the development if built conventionally and the "Cost-With Microgrid" divided by the sum of all rentals plus electricity revenue in Table 10 used. Operating and real estate costs were not considered in the gross time to repay, but it can be assumed that these costs will be identical in both scenarios in any given city.

From Table 11, it can be seen that the gross time to repay initial investment is lower when the microgrid is present. This has positive sociological implications. Since repayment time is shorter, long-term revenue will be higher, making the proposed development model economically profitable and therefore feasible. This has an additional advantage; the charging of premium rents is not economically required due to the lower repayment time of a microgrid inclusive development. The enhanced revenue stream and lowered operating costs associated with building a development around this model would also make affordable housing economically viable, serving to include those who are often left behind and displaced when a neighborhood is redeveloped.

#### 5.3 Environmental impact

Buildings generate greenhouse gases indirectly by consuming electricity produced from various fuels and directly generate such gases through the production of heat and hot water. Table 12 presents the breakdown of fuels used to generate electricity for the local power grid in each of the cities of interest [67]. Table 13 shows the greenhouse gas emissions for each of those sources per kWh [68]. Table 14 presents the percentage of energy derived from renewable sources incorporated into the microgrid in each city of interest. Table 15 contains data on natural gas usage for the development both with and without inclusion of the microgrid. In both cases, annual hot water needs are calculated according to Eq. 7 multiplied by 8760 hr/year, and heating needs are calculated by Eq. 8 multiplied by the number of heating hours estimated in each city from Table 6. For the traditional version of the development, it is assumed that these needs will be supplied by burning natural gas, although less environmentally friendly fuel oil could also be used. When the microgrid is present, heat and hot water needs are met first by trigeneration waste heat, and any unmet needs are met by the same natural gas feed that would fuel the gas turbines. Finally, Table 16 compares the calculated greenhouse gas emissions between the two scenarios with data from Tables 8, 13, 14 and 15.



Estimated rental and electrical rates and annual revenues per source.

City Oil NG Coal Nuclear Hydroelectric Non-hydroelectric renewables

City Oil NG Coal Nuclear Hydroelectric Nonhydroelectric renewables

Lbs/BTU Coal Oil NG Solar Hydroelectric Nuclear Wind CO2 2.15E-04 1.61E-04 1.17E-04 2.89E-05 1.54E-05 7.70E-06 7.10E-06 SO2 2.59E-06 1.12E-06 7.00E-09 Negligible Negligible Negligible Negligible

Total 1.73E+08 1.75E+08 1.76E+08 1.77E+08 1.72E+08 1.73E+08 1.71E+08 1.76E+08 Wind 2.47E+06 7.62E+05 2.17E+06 1.74E+06 2.06E+06 1.70E+06 2.26E+06 2.01E+06

+07

Renewable 18.1% 19.6% 19.3% 20.6% 17.3% 18.3% 17.7% 20.0%

City

2.76E+07 2.99E+07 2.81E+07 3.32E+07

NYC Sao

Paolo

KwH/year Cairo Lagos Shanghai Mumbai London Mexico

Solar 2.89E+07 3.35E+07 3.18E+07 3.48E

Percent renewable power generation on microgrid.

Cairo 44.67% 50.72% 0.47% 0.00% 3.49% 0.65% Lagos 42.12% 28.25% 21.80% 0.82% 5.87% 1.14% Shanghai 18.95% 6.20% 61.83% 1.58% 8.62% 2.82% Mumbai 29.38% 6.23% 56.91% 1.18% 4.03% 2.27% London 38.89% 36.70% 5.83% 8.63% 0.65% 9.31% Mexico City 44.41% 43.20% 5.26% 1.28% 3.63% 2.21% NYC 0.00% 44.00% 1.00% 31.00% 19.00% 5.00% Sao Paolo 46.61% 11.06% 5.55% 1.21% 29.19% 6.38%

Cairo 44.67% 50.72% 0.47% 0.00% 3.49% 0.65% Lagos 42.12% 28.25% 21.80% 0.82% 5.87% 1.14% Shanghai 18.95% 6.20% 61.83% 1.58% 8.62% 2.82% Mumbai 29.38% 6.23% 56.91% 1.18% 4.03% 2.27% London 38.89% 36.70% 5.83% 8.63% 0.65% 9.31% Mexico City 44.41% 43.20% 5.26% 1.28% 3.63% 2.21% NYC 0.00% 44.00% 1.00% 31.00% 19.00% 5.00% Sao Paolo 46.61% 11.06% 5.55% 1.21% 29.19% 6.38%

Microgrids: Applications, Solutions, Case Studies, and Demonstrations

DOI: http://dx.doi.org/10.5772/intechopen.83560

Table 11.

Table 12.

Table 13.

Table 14.

15

Electric power generation source fuels.

Electric power generation source fuels.

Greenhouse gas emissions per source fuel.

Microgrids: Applications, Solutions, Case Studies, and Demonstrations DOI: http://dx.doi.org/10.5772/intechopen.83560


#### Table 11.

Electric power generation source fuels.


#### Table 12.

Electric power generation source fuels.


#### Table 13.

Greenhouse gas emissions per source fuel.


#### Table 14.

Percent renewable power generation on microgrid.

City

14

Cairo Lagos Shanghai

Mumbai

London Mexico City

NYC

Sao Paolo

Table 10. Estimated rental and electrical rates and annual revenues per source.

 \$0.49 \$3.45 \$0.53

\$2.40

\$0.60

\$1.07

\$1.12

\$1.11

\$2.35 \$2.37 \$2.27 \$1.27 \$5.09 \$1.04 \$7.31 \$1.12

\$17.51 \$17.67 \$16.88

\$9.46 \$37.86

\$7.73 \$54.42

\$8.36

\$0.19

 \$8,385,841

 \$15,625,530

 \$14,914,233

 \$3,412,530

\$0.18

 \$54,587,080

\$101,713,358

 \$97,083,212

 \$3,425,333

\$0.08

 \$7,752,948

 \$14,446,245

 \$13,788,630

 \$3,536,433

\$0.22

 \$37,973,621

 \$70,757,118

 \$67,536,148

 \$3,617,546

\$0.07

 \$9,493,405

 \$17,689,280

 \$16,884,037

 \$3,382,754

\$0.09

 \$16,929,906

 \$31,545,882

 \$30,109,866

 \$3,607,725

\$0.08

 \$17,721,023

 \$33,019,989

 \$31,516,869

 \$3,207,401

\$0.02

 \$17,562,800

 \$32,725,167

 \$31,235,468

 \$3,501,974

Micro-Grids - Applications, Operation, Control and Protection

Res./sq. ft./month

 Office/sq. ft./month

 Retail/sq. ft./month

Electricity/kWh

 Res. ent/year

 Office rent/year

 Retail rent/year

Electricity/year


amounts to a 40% drop in potential greenhouse gas production through elec-

Urbanization of populations is occurring at an accelerating pace worldwide, and, in all countries, the increasing densification of population is putting a strain on the pre-existing infrastructure. Depending on the state of national economic development, that infrastructure could be robust, aging, or nonexistent, but was not designed to support the increasing strain. Additionally, this seismic population shift requires housing and employment opportunities in relatively small geographic areas. While growth has always bought opportunity, that opportunity was never immediate or evenly distributed. Hence, slum populations are increasing, and both

History has shown that economies cannot be managed, but it is the job of the government to "promote the general welfare" [69]. At present, various local, national, and international entities are promoting the general welfare through establishing programs to create sociological and environmentally sustainable opportunity. These incentives recognize the existence of a need which can be addressed by a new model of urban growth, one that is economically advantageous and sociologically and environmentally sound, such as the design model proposed herein. The work presented develops a new model for urban development, a model which incorporates a myriad of mature technologies into a real estate development at the design stage. The model bases the development around a self-contained microgrid using trigeneration of power where, at the first stage, fossil fuel-powered turbines produce electricity and heat which, at the second stage, powers a steam turbine to produce more electricity. The third stage of trigeneration is to use the remaining exhaust heat to provide building heat, hot water, and air conditioning. The system is supplemented by renewable solar and wind power, with the buildings designed from the outset to maximize such assets. Modern power storage assets are included in the design to balance the load between times of high usage and low usage.

The study demonstrates that the proposed model succeeds in meeting all sustainability requirements. It is more profitable than constructing the same development on the national power grid. This is vital since economic sustainability is a sine qua non for any urban development. It balances load and generation capability on a large scale, allowing the construction of large numbers of buildings to accommodate increasing populations with essentially no impact on the existing power distribution infrastructure. It is also environmentally sustainable, producing fewer emissions

These conclusions point to the viability and the economic and environmental

desirability of proceeding with urban development under the model herein presented and also lead to a sociological conclusion. Cities are historically built by the poor striving to make a better life for themselves and their families. In developed countries, the consequence of real estate development is too often to push such people out of their homes and further to the fringes. In developing countries, such people are often not even considered, relegated to living in shanty towns. The economic and environmental advantages of this development model present an opportunity to promote the general welfare of all. Environmental financial incentives, coupled with increased profitability, will allow for the maintenance of exceptional living conditions at comparatively low rents. Since renewability and regeneration are incorporated into the building design,

housing and economic opportunity are increasingly scarce.

Microgrids: Applications, Solutions, Case Studies, and Demonstrations

DOI: http://dx.doi.org/10.5772/intechopen.83560

than traditional developments on the same scale.

17

tricity generation.

6. Conclusions

#### Table 15.

NG consumption: with microgrid compared to without microgrid.

These results are significant. As seen in Table 15, a development incorporating a microgrid uses over 10 times the natural gas in all cases than the identical development drawing power from the local distribution grid. However, Table 16 definitively shows that the use of a microgrid would greatly reduce the greenhouse gas emissions from the development, with approximately half of the CO2 and virtually all SO2 emissions eliminated. By incorporating trigeneration from the outset, all upstream emissions from electricity generation are eliminated. Additionally, the use of waste heat in the building systems eliminates emissions from the production of hot water, halves the emissions from building heat, and also eliminates any emissions from air conditioning (bearing in mind that, in a conventional arrangement, air-conditioning emissions would be included in electricity generation emissions). Finally, Table 14 shows that incorporating maximal renewable assets by design accounts for roughly 20% of the electricity production which, at 50% generator efficiency,


#### Table 16.

Comparison of greenhouse emissions for development: without vs. with microgrid.

amounts to a 40% drop in potential greenhouse gas production through electricity generation.
