Grid, pipelines and other infrastructure - DNE21+
|Institution||Research Institute of Innovative Technology for the Earth (RITE), Japan, http://www.rite.or.jp/en/.|
Inter-regional energy transmission infrastructure, such as pipelines for liquid and gas, such as oil, natural gas, synthetic oil, ethanol, hydrogen and CO2, and power grids, are represented in the DNE21+ model.
In terms of systems integration, wind power and solar PV are represented in the DNE21+ model as follows:
(1) Capacity credit:
There are some literatures that evaluate capacity credits of wind power in the United States and Europe (e.g., Milligan and Poter 2008, Holttinen et al. 2009). The estimated capacity credits of wind power vary widely from approximately a few percent to 40% by region. It is also observed that there is a correlation between the capacity credit and the level of technology penetration: the capacity credit becomes lower in higher wind power penetration. When the share of wind power capacity in peak load is 30%, the capacity credits of wind power range from 5% to 25% (Holttinen et al. 2009). In addition, the methods used for the evaluation of the capacity credit exist widely by region, such as capacity factor in peak period and equivalent load carrying capacity.
For solar PV, GE Energy (2010) reported that the capacity credit of solar PV is higher than that of wind power according to the study by the WestConnect group in the United States. In Japan, the capacity credit of solar PV in summer is considered as 16% (Japanese government committee on electricity supply and demand 2013). However, available studies that evaluate the capacity credit of solar PV are limited compared with wind power.
In the DNE21+ model, capacity credit is defined as potential power supplies from wind power and solar PV without electricity storage at the instantaneous peak. Since the peak of these generation does not always match the instantaneous peak time period of power demand, the output of wind power generation at instantaneous peak time is constrained in the model. The capacity credit of wind power is assumed to be 10% in all regions. Although the physical situation for solar and wind energy is different, the same assumption with wind power is applied to solar PV in this paper.
(2) Grid stability
Capacities of wind power and solar PV without electricity storage are limited for the grid stability. In DNE21+, maximum shares in the total electricity supply are 10% both for wind power and PV without electricity storage. Electricity storage systems on the demand side are required for wind power and solar PV to be installed over that shares. If wind power and solar PV are deployed with electricity storage, further 20% of the total electricity supply are available from wind power and solar PV as additional capacities. The capital cost of electricity storage is exogenously assumed to be 1600$/kWh (2005) ? 40$/kWh (2050), presuming rapid technology progress for electricity storage.
Theoretically, the maximum share of wind power and solar PV together in the total electricity generation reaches 60% (10% for wind power without storage, 20% for wind power with storage, 10% for solar PV without storage and 20% for solar PV with storage). The recent large regional wind integration studies in the United States (Milligan et al. 2009) have evaluated wind energy generates up to 30% of annual energy demand. The outlook of electricity generation shares of wind power and solar PV is16% and 20% in 2020 and 2030, respectively, in EU according to the EC communication (EC 2010). The assumed total maximum share is suitable level for energy system assessment until 2050 considering these targets.
The water electrolysis for hydrogen production by photovoltaics has no upper limit, (naturally restrictions on supply of natural resources should be treated separately).