Introduction
Over time, the growth of a city of a locality leads to the increase in the demand for electricity. The growth in population and the commercial activity puts pressure on the national grid. Without commensurate investments in the generation of power, the increase in demand results in shortages. To supplement the shortage of electricity in the region, more power can be brought in from the generation sources. However, this is complicated if the power generation plants are located far away. This is because more high voltage overhead transmission lines would be required. The Ministry for the Environment (2010) finds that the erection of high voltage transmission lines brings with it several risks. Some of the risks include that the safety, health and the well-being of the people and property that are in proximity to the high voltage transmission lines.
In recognition of this risk, Transpower has often discouraged developments in areas in proximity to high voltage transmission lines (Ministry for the Environment, 2010). Several incidents and accidents have occurred that necessitated the consideration of alternatives to the erection of additional transmission lines. For instance, the contact between an irrigator and overhead transmission lines in 2008 resulted in deaths. This incident highlighted the need for sufficient separation distances when overhead transmission lines are erected (Ministry for the Environment, 2010).
Another incident occurred in 2009 when the 220 kV Otahuhu-Whakamaru line experienced a joint failure. As a result of the failure, the overhead line detached and fell on a residential area. Even though only sixteen houses were damaged, the risk to the safety and health of the people in Auckland was high. This incident highlights the importance of the actions by Transpower to discourage development of human settlement beneath the high voltage transmission lines (Ministry for the Environment, 2010).
The incidents and accidents above reiterate the decision by Transpower to explore alternatives to the erection of additional transmission lines to meet the electricity demand in Auckland. This paper will propose various alternatives that can be explored either individually or in combination to alleviate the shortage of electricity in Auckland without necessarily erecting new overhead high voltage transmission lines. The transmission alternatives are aimed at increasing efficiency on both the demand and supply side.
Alternatives to the Erection of Additional Transmission Lines
The electricity transmission grid’s biggest load center in New Zealand is in Auckland. Relative to the power generation sites in New Zealand, the location of Auckland is remote. Thus, a 220kV/110kV overhead transmission line brings electricity to supply the demand for Auckland and the other regions that are located northwards of Auckland (Sinclair Knight Merz, 2005). In the face of the constraints faced by this line, the following alternatives should be explored to negate the need for the erection of transmission lines.
Demand Side Management
Demand side management presents one of the alternatives that be used to delay the need for investments in the erection of addition transmission lines. The concept of demand side management entails the application of measure by the users of electricity to improve efficiency in the utilization of electricity as well as the reduction of the demand for electricity (Energy Efficiency and Conservation Authority, 2005). Demand side management also entails the use of measures that are viable in the short-term as well as measures that ensure the reduction in the demand for electricity in the long-term. This ensures that the gains made in the reduction of electricity demand are sustainable even with the continued growth and development of Auckland (Energy Efficiency and Conservation Authority, 2005). There are various measures that can be employed in the spirit of demand side management. Some of them include the following:
End-use Efficiency
End-use efficiency entails the application of measures that encourage efficiency in the use of electricity for various end uses. Based on the power consumption characteristics of various households and commercial establishments, various end uses that have the potential for significant reductions in the demand for power can be identified. Significant improvements in energy efficiency can be made resulting in a reduction in the energy demand through the insulation of homes to reduce the energy needed for heating and cooling during the winter and summer respectively. This is a strategy that has been recognized during the policy formulation process by New Zealand Government (2007).
Figure 1 below shows that space heating consumes the most energy. This relates to the heating of houses during the winter months and the sections of the day when the temperatures are low. This validates the prioritization of insulation and retrofitting of homes. By insulating and retrofitting the homes, the need for space heating will be significantly reduced. This will contribute to a reduction of the 34% consumption of energy for space heating. Hot water heating is also shown to contribute significantly to the energy demands of residential homes. This also presents an opportunity for the reduction in energy demand by improving energy efficiency in the use of energy for hot water heating. The paragraphs below highlight the measures taken by the government to prioritize these areas to improve end-use energy efficiency.
Figure 1 showing the total energy by energy use in New Zealand
Source: (New Zealand Government, 2007).
The policy response is the provision of interest-free loans for 70,000 people willing to insulate their homes. This is a target had been set to be achieved by 2015. Further improvements in energy efficiency leading to a decrease in energy demand can be achieved through the retrofitting of homes. The recognition of the viability of this approach has also led to policy responses that were aimed at achieving insulation retrofits for 65,000 owners of homes in the low-income family segment by 2012 (New Zealand Government, 2007). The heating of water in residential homes contributes significantly to the utilization of energy. This is more the case when electricity is used to heat the water.
This presents an opportunity for further improvements in energy efficiency. For instance, the use of electricity for heating water can be replaced by the use of solar energy. In recognition of the potential for demand reduction through improved energy efficiency, the policy responses resulted in a target to achieve the installation of between fifteen thousand and twenty thousand solar water heating systems (New Zealand Government, 2007). The achievement of this target was to be evaluated in 2010 (New Zealand Government, 2007). The use of solar energy in heating water for domestic use helps reduce the demand for energy.
The above strategies are very viable for the achievement of end-use energy efficiency because the serve this need in the short-term as well as in the long-term. It is a sustainable approach that can be implemented to achieve the desired reduction in energy demand in a cost effective manner. More importantly, the approach is designed to capacity build the users of electricity to transform their homes to become energy efficient without requiring expensive capital investments from the government. This allows the availability of funds to funds the other installations that are required for the success of the non-transmission alternatives.
The pursuance of energy efficiency is not just limited to residential homes. Energy efficiency in the commercial sector also has the potential to reduce the energy demand. This is achieved through offering incentives to industries and other commercial establishments in Auckland to invest in energy efficient appliances and equipment for their businesses (New Zealand Government, 2007). This has a double whammy benefit. In addition to reducing the energy demand, it also helps reduce the cost of production for the businesses by reducing the energy bills.
For instance, the New Zealand Government (2007) encouraged commercial establishments it invest in changing their motors towards the addition of modern motors that are energy efficient. Part of this move also entails the replacement of industrial lighting and heat processes with more energy efficient ones. Various incentives can be used to encourage the commercial sector to embrace technology transfer and energy efficiency. For instance, after an energy audit, tax reliefs can be given to commercial establishments that achieve given measures of energy efficiency. The achievement of energy efficiency in both the residential sector and commercial sector will contribute significantly to reducing the energy demand, thereby delaying the need for the erection of new transmission lines in Auckland.
It is imperative that measures towards demand side management are sustainable. To enhance sustained energy efficiency in the commercial sector, there is a need to improve the energy efficiency of the new stock of commercial buildings (New Zealand Government, 2007). This can be achieved by instituting a building code that features stringent regulations on the performance of systems such as heating, ventilation, and air conditioning as well as lighting. This will ensure that the newly constructed commercial buildings are more energy efficient (New Zealand Government, 2007).
Load Management
Load management is a response to the fact that the demand for electricity in Auckland differs at various points during the day. There are peak periods when the demand for electricity is highest. It is during these times that some of the shortages in the supply of electricity are witnessed. Load management requires an understanding of the period of the day when the load demand is highest. Load management also requires and understanding of the seasons when the load demand is highest and how various weather patterns affect the transmission ratings. This will enable the evidence-based creation of periods when various peak loads can be shifted.
Load management is a viable alternative to the erection of additional transmission lines because the additional electricity that would be required to suffice the increased demand during the peak times is not needed for the biggest part of the day. For instance, in 2003, the load for Auckland surpassed the 1700 megawatt level on 33 days during the months of July, August, and September (Sinclair Knight Merz, 2005). The load exceeded the 1700 megawatt level mostly during the evenings of weekdays (Sinclair Knight Merz, 2005). The assessment of the load requirement showed that it was only for 4.5 hours that the load in Auckland during this period exceeded the 1700 megawatt level for a consecutive period (Sinclair Knight Merz, 2005). These statistics show that the investment in increased capacity is not economically viable because the increased capacity is only needed for a short period during select sections of the day.
Load management is already being used to good effect in New Zealand. Vector Limited (2016) is one of the organizations that have developed networks through which load management can be implemented. The load management by Vector Limited (2016) is performed during the months of winter. The load demand is usually high during the winter months because of the utilization of electricity for space heating and water heating systems. Vector Limited (2016) reports that load management is necessary during the morning hours and early in the evening.
During this time, Vector Limited (2016) sends a signal that is configured to switch off the appliances for hot water heating. The effect is that the amount of electricity that is used at the time is reduced significantly. The system is constantly monitored to assess the easement in the demand for electricity. It is at this time when the water heating systems are turned on through a signal from Vector Limited (2016). The load management plans offered by Vector Limited (2016) also provide incentives for the users on the plan to stay as well as incentives to attract new customers.
For instance, Vector Limited (2016) reports that the line charges for the customers who are enrolled in price plans that allow for load management for their water heating appliances by Vector Limited (2016) are charged a lower price compared to their counterparts who are not enrolled in such plans. There are further incentives in that even though Vector Limited (2016) limits load management to the months of winter; the decreased prices apply the entire year. This means that overall, the electricity bills paid by these customers are lesser compared to the energy bills of the customers who are not enrolled in the pricing plan that allows load management.
Shunt Capacitive and Inductive Compensation
As noted by Sinclair Knight Merz (2005), Auckland is remotely located relative to the energy production sites. Thus, electricity is transmitted to Auckland through overhead high voltage transmission lines. Due to the length of the transmission lines, there is the element of a deteriorating power factor. The lag load current that occurs results in a lag in the power factor. This is more the case when the transmission line that brings electricity to Auckland is connected to an inductive load. The installation of a shunt capacitor can remedy the situation.
Figure 2 showing the variable shunt reactor
Source: Penton (2016).
Depending on the amount of power factor lag and the length of the transmission line, the type of shunt capacitor required can be determined. The shunt capacitor helps improve the power factor (Chakrabarti, 2010). Shunt inductive compensation can also be used to manage low loads in Auckland by amplifying the voltage. The overall effect of shunt inductive compensation can increase the voltage that is received in Auckland by two times the voltage that was sent from the power production site. Singh (2010) finds this to be a very viable approach, especially in places where the electricity is supplied through long transmission lines.
Generation of Energy
One of the direct ways to meet the constraints in the supply of energy is the generation of more energy. The generation of new energy will help meet the demand for energy in Auckland. Through the concept of distributed generation, Auckland can benefit from the active utilization of solar energy. A study performed by Byrd (2012) to determine the potential for the generation of energy using solar power in Auckland found a large untapped potential. In the midst of transmission inefficiencies due to the remote location of Auckland relative to the power generation sites, the use of distributed generation of electricity can help reduce the peak electricity demand in Auckland.
In addition, Byrd (2012) found that distributed generation of electricity can also help reduce the utilization of energy for transportation and also solve the transmission inefficiencies that predict the shortages of power in Auckland. This approach entails the installation of photovoltaic cells on the buildings to exploit the solar energy to generate electricity that can be used in the residential homes for various end uses. The success of this approach is dependent on the mass implementation of the recommendation for the installation of photovoltaic cells.
The needs assessment performed by Byrd (2012) highlighted some of the characteristics that make Auckland an ideal city for the implementation of distributed generation of electricity. Firstly, the yearly solar radiation levels for Auckland as a high as other cities that benefit immensely from distributed generations such as Los Angeles and Barcelona (Byrd, 2012). Secondly, the design of the city of Auckland is dispersed rather than compact. This makes the generation of electricity using photovoltaic cells very viable. The commercial and residential houses in Auckland also use heating, ventilation, and air conditioning systems. This results in an increase in peak electricity load during the summer months (Byrd, 2012).
However, the success of this alternative is dependent on the introduction of a subsidized feed-in-tariff. This offers an incentive for the uptake of photovoltaic cells for the generation of electricity by both residential and commercial users (Byrd, 2012). The surplus electricity can be sold to Transpower at an agreed price. The surplus electricity can then be fed into the national grid for transmission to other areas or use within Auckland for other end uses. This alternative is in keeping with the trends in power generation in New Zealand. Byrd (2012) finds that over 75% of the energy that is used in New Zealand is generated from renewable sources. The success model can be replicated through distributed generation to meet the increased demand for energy in Auckland thereby averting the need for the erection of new transmission lines to bring in power from the power generation sites.
Conclusion
The continued growth of Auckland has led to an increase in the demand for electricity. The remote location of the city relative to the power generation sites also works to its disadvantage because the long transmission lines that bring in power are prone to inefficiencies that manifest through reduced voltage and load. The erection of new transmission lines to augment the power deficits requires significant capital investments. However, there are non-transmission alternatives that can be implemented to meet the energy deficits. One of the alternatives is the improvement of end-use efficiency for both residential and commercial end users. Additionally, load management can be implemented for the hours of the day when there is peak electricity demand. This is an approach that has already been implemented with a lot of success. Alternatively, the capacitive and inductive shunt compensation of the long transmission lines can be implemented to amplify the voltage and reduce the power factor lag respectively. Transpower can also encourage the distributed generation of electricity through the installation of photovoltaic cells in both residential and commercial buildings.
References
Byrd, H. (2012). The solar potential of Auckland. Retrieved from http://eprints.lincoln.ac.uk/17428/1/Solar-potential-booklet.pdf
Chakrabarti, A. (2010). An introduction to reactive power control and voltage stability in power transmission systems. New Delhi: PHI Learning Private Ltd.
Energy Efficiency and Conservation Authority. (2005). Energy Efficiency and Conservation Authority: Commentary on Demand Side Management and Renewable Generation Alternatives to the Auckland Transmission Upgrade. Retrieved from https:// www.ea.govt.nz%2Fdmsdocument%2F4681
Ministry for the Environment. (2010). National Policy Statement on Electricity Transmission: Further Guidance on Risks of Development near High-voltage Transmission Lines. Wellington: Ministry for the Environment.
New Zealand Government. (2007). New Zealand Energy Efficiency and Conservation Strategy. Retrieved from http://www.otago.ac.nz/oerc/research_output/govt_documents /nz_energy_strategy_2007.pdf
Penton (2016). Balance of power. Retrieved from http://tdworld.com/sponsored-articles/balance- power
Sinclair Knight Merz. (2005). Auckland’s electrical demand characteristics and applicability of demand management. Retrieved from https://www.ea.govt.nz/dmsdocument/4751
Singh, S. N. (2010). Electric power generation, transmission and distribution. New Delhi: PHI Learning.
Vector Limited. (2016). Reducing load on our networks during peak periods. Retrieved from https://vector.co.nz/electricity/load-management.
