Introduction
In recent timess, there has been significant buzz surrounding battery storage for solar power projects in Nepal. Some industry observers believe the recent introduction of the “take and pay” mechanism for Run-of-River (RoR) hydropower projects is part of a broader shift aimed at prioritizing solar power coupled with battery storage. This prompted me to analyze how battery-backed solar stacks up against traditional RoR hydro and peaking RoR projects in terms of energy supply during critical demand periods.
Typical Energy Generation from a 1 MW RoR Project
Below is a typical monthly energy generation table for a 1 MW RoR hydropower project in Nepal:
Month | Days | Power (kW) | Montly Net Energy Generation (kWh) | Daily Energy Production (kWh) | Hourly Energy Production (kWh) |
January | 31 | 475.87 | 339,886 | 10,964 | 457 |
February | 28 | 378.85 | 244,404 | 8,729 | 364 |
March | 31 | 262.80 | 187,700 | 6,055 | 252 |
April | 30 | 363.59 | 251,311 | 8,377 | 349 |
May | 31 | 398.61 | 284,703 | 9,184 | 383 |
June | 30 | 958.53 | 662,536 | 22,085 | 920 |
July | 31 | 958.53 | 684,621 | 22,085 | 920 |
August | 31 | 958.53 | 684,621 | 22,085 | 920 |
September | 30 | 958.53 | 662,536 | 22,085 | 920 |
October | 31 | 958.53 | 684,621 | 22,085 | 920 |
November | 30 | 851.41 | 588,495 | 19,616 | 817 |
December | 31 | 636.36 | 454,517 | 14,662 | 611 |
Total | 365 | | 5,729,948 | | |
Wet | 3,967,429 | 69.24% | |||
PLF | 65.4% | Dry | 1,762,519 | 30.76% | |
Total | 5,729,948 | 100.00% |
This data shows that a 1 MW RoR plant generates at full or near-full capacity during the wet season, while its generation drops significantly during the dry months ranging from 611 to 252 kWh per day per hour. Importantly, a RoR plant typically operates continuously, providing a steady supply of electricity 24 hours a day, regardless of the season. It is noteworthy to mention that 4% outage is considered while calculating the energy which is a standard requirement.
Typical Energy Generation from a 1 MW Solar Project
Next, consider a typical 1 MW solar PV installation in Nepal:
Month | Days | Montly Net Energy Generation (kWh) | Daily Energy Production (kWh) | Hourly Energy Production (kWh) |
January | 31 | 133,920 | 4,320 | 720 |
February | 28 | 120,960 | 4,320 | 720 |
March | 31 | 133,920 | 4,320 | 720 |
April | 30 | 129,600 | 4,320 | 720 |
May | 31 | 133,920 | 4,320 | 720 |
June | 30 | 129,600 | 4,320 | 720 |
July | 31 | 133,920 | 4,320 | 720 |
August | 31 | 133,920 | 4,320 | 720 |
September | 30 | 129,600 | 4,320 | 720 |
October | 31 | 133,920 | 4,320 | 720 |
November | 30 | 129,600 | 4,320 | 720 |
December | 31 | 133,920 | 4,320 | 720 |
Total | 365 | 1,576,800 |
Unlike hydropower, solar production is inherently intermittent. The table assumes an annual average of six productive sunlight hours per day. This means that while a 1 MW solar plant can generate consistent daily output under ideal conditions, it produces no electricity at night and fluctuates with weather conditions. So comparing solar with RoR make no sense as solar does not produce energy when needed.
Key Consideration: The Role of Battery Storage
The recent interest in battery-backed solar projects is not about seasonal energy storage (e.g., storing wet season energy for use in the dry season) — which would be prohibitively expensive for grid-scale deployment. Rather, the main purpose is to store solar generation during daytime and discharge it during peak demand hours on the same day. So it is actually not comparable to storage, it's more like a peaking.
Peaking Run-of-River: An Alternative Peaking Solution
To compare with battery-backed solar, I modeled a scenario where a typical RoR plant is converted into a peaking plant — assuming the river topography allows short-term water storage. Below is the peaking energy supply profile:
Month | Days | Daily Dry Peak (kWh) | Daily Dry Off Peak (kWh) | Daily Wet Energy (kWh) | Hourly Dry Peak (kWh) | Hourly Dry Off Dry (kWh) | Hourly Wet Energy (kWh) |
Jan | 31 | 6,055 | 4,909 | - | 917.40 | 204.55 | - |
Feb | 28 | 6,055 | 2,674 | - | 917.40 | 111.41 | - |
Mar | 31 | 6,055 | - | - | 917.40 | - | - |
Apr | 30 | 6,055 | 2,322 | - | 917.40 | 96.76 | - |
May | 31 | 6,055 | 3,129 | - | 917.40 | 130.38 | - |
Jun | 30 | - | - | 22,085 | - | 920 | |
Jul | 31 | - | - | 22,085 | - | 920 | |
Aug | 31 | - | - | 22,085 | - | 920 | |
Sep | 30 | - | - | 22,085 | - | 920 | |
Oct | 31 | - | - | 22,085 | - | 920 | |
Nov | 30 | - | - | 19,616 | - | 817 | |
Dec | 31 | 6,055 | 8,607 | - | 917.40 | 358.62 | - |
Total | 365 |
This demonstrates that, during dry months, a 1 MW peaking RoR plant can deliver near-full capacity for around 6.6 hours daily, focusing supply during peak demand periods.
Battery-Backed Solar: Daily Peaking Capability
For battery storage, I assumed a discharge rate designed to balance performance and battery lifespan (0.25 C), resulting in approximately four hours of high-capacity supply daily. The table below illustrates the same:
Month | Days | Montly Net Energy Generation (kWh) | Daily Energy Production and stored (kWh) | Per hour supply (4 hours discharge time) kWh |
January | 31 | 133,920 | 4,320 | 1,080 |
February | 28 | 120,960 | 4,320 | 1,080 |
March | 31 | 133,920 | 4,320 | 1,080 |
April | 30 | 129,600 | 4,320 | 1,080 |
May | 31 | 133,920 | 4,320 | 1,080 |
June | 30 | 129,600 | 4,320 | 1,080 |
July | 31 | 133,920 | 4,320 | 1,080 |
August | 31 | 133,920 | 4,320 | 1,080 |
September | 30 | 129,600 | 4,320 | 1,080 |
October | 31 | 133,920 | 4,320 | 1,080 |
November | 30 | 129,600 | 4,320 | 1,080 |
December | 31 | 133,920 | 4,320 | 1,080 |
Total | 365 | 1,576,800 |
This means that, operationally, a 1 MW solar system with a properly sized battery can supply about 1,080 kWh per hourfor four peak hours daily — exceeding the per-hour peak supply of a 1 MW peaking RoR during the dry season. But when it is compared with Peaking RoR, the peaking RoR supplies 917.40 kWh per day per hour during dry season for 6.6 hours whereas solar supplies 1,080 kWh per day per hour for 4 hours.
Key Observations
Several important points emerge from this comparison:
- Longevity: Hydropower plants generally have operational lifespans exceeding 50 years and are typically transferred to government ownership after 30 years, ensuring long-term national benefit.
- Land Use: Solar projects require significant land area (25–30 ropanis per MW in Nepal) and most sites are leased, adding long-term cost and site security considerations.
- Sustainability: While solar with storage offers flexibility for daily peak demand management, it does not replace the role of hydro in providing baseload and seasonal storage.
Conclusion
While battery-backed solar projects show clear advantages for daily peak energy supply as compared to RoR project, their role is complementary rather than substitutive to hydropower. RoR hydropower — especially if upgraded for peaking operation — continues to be indispensable for Nepal’s energy security, sustainability, and long-term economic returns.
Understanding these systems is vital as Nepal navigates its path towards a resilient, diversified, and clean energy mix.
No comments:
Post a Comment