3.5 Work required to facilitate high penetration IRG

The literature suggests further research is necessary to assist in the transition to high penetration IRG. Areas include forecasting, acquisition of high resolution data on irradiance and PV output, and load profiles. Detailed studies on energy storage and a review of standards to integrate more IRG into grid operations are also mentioned.

The following future work is suggested in [22]:

  • Developing models representing aggregated behaviour of PV and updated transmission planning databases to accommodate such models. This is reiterated in [13]
  • Improve understanding on the role PV can play at the distribution and transmission level to quantify performance and economic impact on regulation and load-following. This would include required flexibility of non-variable generation. A dispatch strategy could be developed once PV behaviour is well understood
  • Quantifying the economic and performance benefit of mitigating variability of PV.

Customer load statistics are deemed important in [23]. Detailed load profile data for individual homes would allow for accurate modelling on the impact of PV and storage. The results of such modelling would be a reliable basis from which to gauge the economic viability of PV and storage.

It is suggested in [13] to look in to standards, claiming there need to be concise and comprehensive practices and standards developed to handle distributed PV, making the process of further penetration easier. Also necessary for the uptake of high penetration solar power are:

  • further simulation to determine the impact on power quality (voltage, etc.) and fault contribution of inverter connected PV
  • pilot programs to test communication between centralised control, distributed PV and protection devices using the Internet
  • quantifying the variability of the renewable resource, to determine the amount of flexibility required by the system
  • modelling requirements: grid behaviour due to changes in insolation, Var support, dynamics of anti-islanding detection and fault response.

Models to accurately and comprehensively describe the behaviour of large scale solar plants are also required, as is developing leading-edge solar forecasting [6].

The effective identification of grid locations best suited for PV installations at the distribution level should take into account:

  • power quality impacts, or if the potential installation contributes to grid stability
  • coincident load/generation load profiles
  • grid impedance
  • offsetting of transmission line upgrades.

3.5.1 Data

High resolution insolation data, time synchronised across different spatial scales, is required for analysts to develop projections of intermittent renewable generation [12]. This is required as there will be different impacts requiring different responses at different spatial scales, including:

  • large individual plants (1-10s km2)
  • dispersed PV plants connected to the same feeder (10-100s km2)
  • aggregate of all PV generation across the balancing area (1000-10000s km2).

To understand how regulation will be impacted, data will need to be gathered at high resolutions of up to 10 seconds, and synchronised with load data, to give a clear picture of the net impact of varying load and generation. Data will need to be gathered for a period of at least a year.

Cross-disciplinary analysis projects are considered important as stated in [11]; “The use of solar resource and meteorological data to address complex problems such as time-dependent utility load estimations, cloud transient effects on grid stability, and solar dispatching require close collaboration between analysts and utility planners, and the resource and meteorology community”

Weather systems can cover very large areas, reducing the advantages gained from an increased load balancing area. According to [18], studies are required to determine the correlation of weather across the spread of the electricity grid -ensuring links between areas with weak weather pattern correlation.

3.5.2 Energy storage and load response

Investigation into energy management systems (EMS) is suggested in [20]. Algorithms, hardware and communication protocols (between utilities, DG and distributed storage) will need to be developed to optimise the use of energy sources. A well designed EMS will store energy when prices are low and inject power when prices are high or when auxiliary support (for voltage regulation for example) is requested. If they prove to be commercially viable, private sector investment could see a proliferation of such systems. Energy storage systems which can be integrated with PV also need to be identified. In aggregate, these systems could be utilised for ancillary services.

To assess how distributed energy resources, in particular residential air-conditioning, could provide a responsive spinning reserve capacity, Lawrence Berkeley National Laboratory (coordinated by the Consortium for Electric Reliability Technology Solutions) carried out the Demand Response Spinning Reserve project. The demonstration showed it is technologically feasible to provide a spinning reserve ancillary service through demand-side resources. This could become a preferred option, since the response is near instantaneous.