Introduction

The Nova Scotia Utility and Review Board is conducting public hearings into the franchising of natural gas distribution in the province of Nova Scotia. The franchisee who wins the distribution rights will sell the gas to customers around the province. Many customers, primarily residential and commercial, will use the natural gas for space heating and (domestic) hot water.

This paper presents the argument that despite its 'cleanliness' (when compared to other fossil fuels), natural gas is still a finite resource and, as such, should be used as efficiently as possible. Low-grade heating (i.e., space heating and hot water) are not examples of the efficient use of any fossil fuel, especially natural gas. Nor, for that matter, is Nova Scotia Power's current policy of disposing of 'waste' heat from its thermal power stations into large bodies of water.

Rather than using natural gas for low-grade heating, the author proposes that the province's natural gas be consumed in combined heat and power (or CHP) stations that would generate both electricity and low-grade heating water. The low-grade heating water would be transported in insulated pipes from the CHP station to nearby customers using a technique known as district heating. District heating is less costly and more environmentally friendly than existing energy systems that generate electricity and low-grade heating separately.

Although district heating has made limited penetration in Canada, it is found in most Scandiavian urban centres and parts of the former Soviet Union (FSU). In fact, when natural gas was discovered in Denmark's sector of the North Sea, new homes were connected to district heating stations rather than to the natural gas network.

Analysis

The following section presents a brief calculation which demonstrates the potential of district heating when used in conjunction with a power station such as Tuft's Cove.

Tuft's Cove is rated at 350 MW (megawatts, or one million watts), which means the station produces about 350 MW of electricity. Assuming that Tuft's Code has a 30 per cent capacity factor (i.e., for every 10 units of energy consumed, 3 units of electrical energy are generated -- typical for most thermal stations), then the station requires about 1160 MW of its fuel source (at present, oil, soon to be natural gas). Since the station produces only electricity, the equivalent of 810 MW of heat is discarded (1160 MW minus 350 MW) into the environment (primarily Halifax harbour).

According to Nova Scotia Power, the peak hour heating requirements for an 'average' home in Nova Scotia is 12 kw (kilowatts, or one thousand watts). The number of homes that could be heated by the 'waste' heat from Tuft's Cove would depend upon how much of the waste heat is used. Table 1 shows the maximum number of dwellings that could be heated, based upon the percentage of waste heat used; for example, if 30 per cent of the total available energy (1160 MW) is used, some 348 MW of heating water is available, which could heat some 29,000 dwellings.

The number of dwellings in the metropolitan Halifax area is shown in Table 2: Halifax has the greatest number of dwellings (50,475) and the highest density (637). Depending upon the amount of heat available to the district heating system, it would be possible to heat all of Dartmouth (at the 30 per cent level) or all of Halifax (at the 60 per cent level) or some combination of the two.

District heating vs natural gas

The construction of a natural gas network within a city will be similar in scope to the construction of a district heating network. District heating differs in that the piping is slightly larger and insulated. With the exception of district heating systems in the FSU, most systems support a closed loop, with the cooled low-grade heat water returning to the power station.

Unlike a natural gas system, there is no 'furnace' in buildings connected to a district heating system. Each building is connected to a heat exchanger that extracts the required amount of heat from the district heating system.

In many countries, district heating systems 'grow' by building small heating plants in one part of the community and connecting the small system to the larger system over time. For security purposes, district heating systems may be a combination of interconnected, independent CHP stations; should one fail, others can carry the load during the breakdown.

Summary

In summary, the author believes that district heating should be the heating source of choice for the residents of Halifax for the following reasons:

• Safety. The effects of a district heating pipe failing are minimal compared to that of a gas main failure.

• Health. District heating can be healthier than natural gas because there is only one 'smokestack' in a neighbourhood (as opposed to each dwelling having its own); it is easier to fit pollution control devices on a single, communal smokestack than on all the chimneys in a neighbourhood.

• Energy efficiency. Generating electricity from natural gas and heating homes with natural gas is less efficient than generating electricity and heating homes with fewer units of natural gas.

• Carbon dioxide emissions. Natural gas emits the least carbon dioxide per unit of energy of any other fossil fuel and, as a result, Nova Scotia's CO2 emissions would decline. These emissions would decline even further if district heating were adopted.

• Fuel costs. At present, Nova Scotia Power treats the cooling water from Tuft's Cove as a 'waste' product, dumping it into Halifax harbour. If Nova Scotia Power were to sell this 'waste' heat to residential and commerical clients, the price of electricity could fall, since a former 'waste' product would now be generating revenue for the company. It should be noted that Nova Scotia Power and Tri-Gen are working on a steam heat system for large commerical and governmental clients in Halifax. Although this is clearly a start, it only utilizes a fraction of the available energy from Tuft's Cove.)

• Long term future. In 20 or so years, it is predicted that the Sable natural gas fields will be exhausted; if this is the case, then Halifax will have an unusable vast underground natural gas network; this network cannot be used with hydrogen, nor can it be used for district heating. However, if a district heating network were put in place now, the fuel source at Tuft's Cove could change (for example, to biomass), but the end product, heating water, would remain unchanged.

In light of the above, the author urges the Utility and Review Board to reconsider the proposals for the distribution of natural gas in the metropolitan Halifax area. Rather than franchising natural gas distribution for the production of low-grade heat, the Utility and Review Board should look for companies willing to support the development of provincial district heating systems.

Although metropolitan Halifax and Tuft's Cove were used as an example, the same arguments apply to any community in Nova Scotia situated near a power station. Furthermore, with the advent of electrical deregulation, small electrical power producers could 'tap' into the provincial natural gas network with highly efficient CHP stations in towns scattered throughout the province, producing both electricity for export and heat for local consumption.

Sable natural gas is a gift to the citizens of Nova Scotia, it should be use as wisely and efficiently as possible.

© 1999 -- Whale Lake Press