Energy generated by intermittent renewable sources (solar and wind) is vulnerable to large fluctuations, as their force and occurrence at a defined site cannot be controlled. Un-forecasted solar and wind power fluctuations can therefore increase spinning reserve requirements, and drive up the electricity generation costs. Further, large ramp events such as thick cloud cover can affect power system frequency stability.
In Pakistan, opponents of renewable energy frequently cite the intermittency issue to justify adding coal and RLNG plants into our energy mix instead of solar and/or wind. However, with the improvement in technology, this intermittency issue is now manageable and can no longer be used as an excuse for not increasing the share of solar and wind energy.
Given below are the various ways, the policy makers and the system and grid operator can address the intermittency issue:
Combining wind and solar projects in the same location can increase the aggregate system output by making optimal use of sunlight and wind energy. As such, the cost of the resultant hybrid systems will be substantially lower.
Another advantage of the hybrid systems is that grid expansion is not required for such types of power plant, as the power is generated from wind and solar, at different times and in in different seasons. Due to this advantage, the level of energy that is injected into the grid by the hybrid plants is steadier than that of wind or solar photovoltaic alone.
Hybrid plants are also ideal for installation in remote areas, electrifying complete regions with high efficiency. Given the low electrification rates and high availability of both wind and sunlight in Balochistan and Sindh, hybrid plants (solar–wind, solar–wind–diesel, solar–diesel) are ideal for powering off-grid areas where grid extension would be technically and financially infeasible.
For broader implementation, AEDB should conduct a baseline study to identify locations, across the country, for grid-connected hybrid plants. Moreover, the government would have to introduce policy and regulatory measures specifically for hybrid projects. Lastly, NEPRA needs to devise new formula and procedures for a single tariff for hybrid projects.
Battery storage is particularly well suited for smoothening the variable output of renewables and controlling the rapid ramping up and down of solar and wind generation.
Combining battery storage with renewable energy can support the output of these plants by responding quickly to any output fluctuations. It stabilizes wind and photovoltaic output in low, medium, and high voltage by providing frequency control fluctuations. Batteries are also being used for providing emergency backup in the event of an outage.
Lithium-ion battery costs have dropped since 2015. For peaking plant replacement, lithium-ion batteries now ranges from $285 to $581 per megawatt-hour (MWh), compared with last year when it was between $321 and $658 per MWh. The cost of lithium-ion batteries also fell 24% for the transmission use case and 11% for residential. Its lowest-cost use is for frequency regulation, where the minimum cost fell from $211 per MWh last year to $190 per MWh.
Energy storage offers a clear opportunity for a developing country like Pakistan to leapfrog over old technologies to improve system reliability, and use existing infrastructure in an optimal manner. However, changes in regulatory and policy frameworks will be required for incentivizing deployment of energy storage technologies in the country.
Solar and Wind Forecasting
Integrating solar and wind energy successfully into the system requires high-quality weather predictions. Forecasting their output days, hours, and minutes in advance can significantly lower grid operation costs and balancing power demand.
Short-term renewable energy forecasting is also an essential tool for operating power systems to show the impact of large penetration of solar or wind generation on spinning reserve requirements.
In Pakistan, National Transmission and Despatch Company needs to work with two or three companies in the field of forecasting: one provider to merge all the different data within a software to simulate Pakistan’s’ national grid and the other service provider (specialized in weather forecasting and renewable energy production) to use the latest projection techniques for smooth functioning of grid operations. This would enable the system operator to optimize dispatch of generation capacity based on precise forecasts.
Smart grid technology help address the challenge of variability of renewables as these provide real-time data on system operation enabling more control over the system. This data can be used for improving reliability of the grid as well as for increasing system security.
The technology also allows for more sophisticated information from transmission and distribution systems, which, in turn, improves reliability and reduces system integration costs. Any fluctuation of voltage on either the distribution or transmission system can be addressed before it leads to an outage.
Detailed information on renewables’ performance can also help facilitate the distribution company or the system operator to price distributed renewables more accurately.
Implementation of smart grid in Pakistan can help address many of the technical, economic, and regulatory challenges associated with renewables. The logical path would be to install smart grid technology incrementally through pilot or demonstration projects to see how these perform in a given system. When first implementing smart grid technologies, it would be better to start with distribution automation and demand response
Denmark and Germany have more than 70% of their electricity supplied through wind and solar respectively. China and India have set ambitious targets for integration of solar energy into their power systems.
The time is ripe for Pakistan to benefit from the green energy revolution that the world is witnessing. It is no longer necessary to heavily invest in fossil fuels for achieving high levels of economic growth. The R&D that the world is undertaking in smart grid and storage technologies will soon make it financially viable for a country like Pakistan to benefit from. However, the Government would meanwhile have to ensure that the necessary policy and regulatory policy frameworks are in place.