Renewable Energy Integration, Economic Operation of Grid, Merit order Dispatch, Effective cost of renewables

1. Merit Order Violation Limit of
Renewable Energy Penetration
S.R.Anand

2. Introduction
• Renewable energy is regarded as the source of
energy for future.
• Low environmental impact and the low
gestation period have prompted most of the
governments to enact legislations to promote
the use of renewable sources for production
of electricity

3. Indian Scenario
• India has total estimated renewable energy
potential of about 2,45,880 MW
– Wind-100GW
– Small Hydro–20GW
– Biomass/ Bioenergy-25GW
– Solar -100GW

4. Indications
• Wind, Small hydels, Bioenergy
– Matured – Commercially viable
• Solar
– Gujarat state solar policy (2009), National Solar
Mission (2010)
– Growth rate – 85% for last 4 years
– Distributed Solar
• Grid parity for high ended domestic consumers,
commercial consumers and industrial consumers

5. Global trends – Solar PV
• 16% of global electricity consumption (2013)
• 160 TWh/yr of clean electricity and thus
avoiding about 140 million tonnes of CO2 per
year (2013)
• Growth rate – 49% (100MW/day)
• Forecast - 4 GtCO2/yr of emissions, or 19% of
the total power sector emission reductions by
2050 by Solar PV

6. Solar capability
• The annual yield solar energy - 885 MTWh –
almost 6000 times the commercial primary
energy requirement
• solar radiation reaching the earth’s surface is
about 1 kW/m2 in clear conditions when the
sun is near the zenith
• Annual mean daily global solar radiation in
India - 4.5-6.5 kWh/m2/day

7. Performance Ratio
• Factors affecting efficiency loss
– actual module temperature
– module mismatch
– varying irradiance conditions
– Dirt
– line resistance
– conversion losses in the inverter
• Achievable PR – 80-90%

8. Issues
• Whether the distribution grid is capable of absorbing the
variability of PV generation
• Whether the transmission system reliability is likely to be
affected in the event of simultaneous injection
• Whether the current regulations and technical standards
are sufficient to address the emerging scenario
• What are the safe limits of PV penetration and when that
capacity is reached how to tackle the issue of existing
inefficient system not permitting an efficient system
especially when the assets are owned by private parties
• What are the potential solutions for integrating larger
quantities with equitable distribution of costs to stake
holders

9. Standards and Regulations
• Technical Standards for Connectivity of the
Distributed Generation Resources Regulations,
2013
• Installation and Operation of Meters Regulation
2006 (2013 amendment)
• Measures of Safety and Electricity Supply
Regulations
• Technical Standards for Connectivity of the
Distributed Generation Resources
• IEC Standards for PV modules (IEC 61215 for c-Si,
IEA 61646 for TF, IEC 62108 for CPV modules).

10. Issues addressed
• Germany and Italy have faced technical issues
due to rapid deployment of PV
• In 2012 Germany revised its Renewable Energy
Sources Act to oblige new PV plants to allow
remote curtailment
• Germany’s System Stability Act of May 2012
scheduled the retrofit of PV systems by the end
of 2014
– Power inverters must be able to reduce output when
frequency rises too high or to turn themselves off

11. Technical issues
• Rapid changes in the load seen by the
transmission system
– The load net of PV generation (gross load minus
variable generation from PV and wind) may vary from
minutes up to a timescale of one or two days
• Construction of a transmission and distribution
network much above the requirement
• Additional voltage control devices (FACTS)
– increases the cost of supply

12. Self consumption capability
• In Kerala scenario, most PV electricity generated
by domestic consumers (and generators) during
summer will be self-consumed. On summer
holidays, the self-consumption may be more than
the PV generation for domestic category and vice
versa for commercial/ small industrial consumers
• The load profile of office buildings or
supermarkets is a better match with the solar
resource, which reaches its maximum in the
middle of the day

13. Mitigations
• Inverter Control
– riding through wide ranges of voltage and
frequency fluctuations
– providing reactive power support
– disconnecting and reconnecting softly to avoid
sharp spikes during power outages
– Integration to remote SCADA to sensitivise the
grid requirement

14. Effects that require caution
• replace the marginal generator on merit order
stack with a costly generator with high ramping
capability
• result in sub optimal loading of generators,
especially linked with geographical distribution of
PV and capability of transmission system
• operation of gas turbines in open cycle instead of
combined cycle
• result in frequent start – stops of thermal
generators resulting in increase of O&M costs etc.

15. • Fuel cost function for thermal generating units
Fc (Pi)
𝐹𝑐 = 𝑖=1
𝑁
(𝐴𝑖+𝐵𝑖 + 𝐶𝑖
2
)
• Total demand is given by
𝑃𝑑 =
𝑖=1
𝑁
𝑃𝑖 + 𝑃𝐿

16. • Cost of renewable absorption
𝐶 𝑅 = 𝐹𝐶𝑠 + 𝐶ℎ + 𝐶 𝑑 + 𝐶 𝑅𝐸
Where
𝐹𝐶𝑠 = 𝐹𝑖𝑥𝑒𝑑 𝑐𝑜𝑠𝑡 𝑜𝑓 𝑠𝑢𝑟𝑟𝑒𝑛𝑑𝑒𝑟𝑒𝑑 𝑡ℎ𝑒𝑟𝑚𝑎𝑙
𝐶ℎ = 𝐻𝑒𝑎𝑡 𝑟𝑎𝑡𝑒 𝑐𝑜𝑟𝑟𝑒𝑐𝑡𝑖𝑜𝑛 𝑜𝑓 𝑡ℎ𝑒𝑟𝑚𝑎𝑙
𝐶 𝑑 = 𝐶𝑜𝑠𝑡 𝑜𝑓 𝐷𝑒𝑣𝑖𝑎𝑡𝑖𝑜𝑛
𝐶 𝑅𝐸 = 𝐴𝑐𝑡𝑢𝑎𝑙 𝑐𝑜𝑠𝑡 𝑜𝑓 𝑅𝑒𝑛𝑒𝑤𝑎𝑏𝑙𝑒

17. Typical figures
𝐶 𝑅 = 𝐹𝐶𝑠 + 𝐶ℎ + 𝐶 𝑑
= 2.00 + 0.50 + 1.75
= 𝑅𝑠. 4.25
Effective cost of Renewable energy
𝐶 𝑅 = 𝐶 𝑅 + 𝐴𝑐𝑡𝑢𝑎𝑙 𝑐𝑜𝑠𝑡 𝑜𝑓 𝑟𝑒𝑛𝑒𝑤𝑎𝑏𝑙𝑒
= 4.25 + 3.15 = 𝑅𝑠 7.40 𝑓𝑜𝑟 𝑤𝑖𝑛𝑑
= 4.25 + 5.50 = 𝑅𝑠 9.75 𝑓𝑜𝑟 𝑠𝑜𝑙𝑎𝑟