TY - JOUR
T1 - Advanced energy flexibility enhancement via the novel resources of wave energy converter reservoirs and electric storages for a hybrid wave-wind energy supported hotel energy system
AU - Luo, Haojie
AU - Cao, Sunliang
N1 - Funding Information:
This research is partially supported by the Project ID “P0033880” from Research Institute for Sustainable Urban Development (RISUD), and partially supported by the Project ID “P0039664” from Research Institute for Smart Energy (RISE), The Hong Kong Polytechnic University .
Funding Information:
It studied a zero-energy building (ZEB), a hypothetical simulated hotel located in the coastal area equipped with a hybrid wind-wave energy system, learnt from the previous research for its techno-economic feasibility [35]. The ZEB utilised the OWEC and offshore wind turbine (WT) to support the electric demand for the thermal and electrical systems. Based on the specific electricity pricing scheme, which considers the monthly maximum power demand as well as the on-peak and off-peak energy demands, the first group utilised the battery to conduct energy shifting and valley filling to change the interaction schedule with the electric grid. The second group also investigated flexibility control after the electric load was partly covered by hybrid wind–wave energy. Because of the inherent characteristic of the OWEC's self-integrated reservoir to collect the incident ocean wave, the flexibility of the seawater discharging control, and consequently, of the power generation, was investigated in the third group. It employed a strategy like a reservoir-type power plant stores the wave energy rather than discharging it, as there is no benefit of exporting the surplus energy to the grid. Under this control, which followed the system demand, further introduced battery control to pursue more cost savings. According to the results of the third group, the improper charge was found in some sections of the current electricity pricing scheme. The fourth group proposed a new energy billing model based on the original tariff to maximise the achievement of the flexibility controls. The effects of the flexibility controls were evaluated by operational cost, relative net present value, on-peak peak-shaving indicator, and off-peak valley filling indicators. Two energy matching analysis criteria, on-site electrical energy matching (OEMe) and on-site electrical energy fraction (OEFe) were applied in this study to estimate the extent of the energy matching.The specific pricing scheme for business electricity consumption must first be introduced, called the Bulk Tariff, and established by CLP Power Hong Kong Limited, as the electricity fee is the main operational cost of the target building during the 20-year working period. The monthly electricity tariff is divided into three items, which are demand charge, energy charge, and fuel cost adjustment. The billing demand and energy consumption are separated into on-peak and off-peak periods. The on-peak period is the daily period between 9:00 and 21:00, except for Sunday and public holidays, which are considered off-peak periods [45]. (a) Demand Charge: During the on-peak period, the monthly maximum demand not exceeding 650 kVA should be charged at HKD 68.4/kVA. The minimum on-peak billing demand is 100 kVA, which means the charge will be calculated as 100 kVA even though the monthly maximum demand is below 100 kVA. Meanwhile, there is no demand charge if the monthly maximum demand during the off-peak is lower than the on-peak. If not, anything in excess of the on-peak demand is billed at HKD 26.8/kVA. (b) Energy Charge: The on-peak electricity consumption of fewer than 200,000 kWh is charged at HKD 0.753/kWh, while off-peak consumption at HKD 0.676/kWh. (c) Fuel Cost Adjustment: Based on the forecasted fuel prices in the latest tariff review, the fuel cost adjustment is HKD 0.0281/kWh for both on-peak and off-peak consumption [45]. Therefore, the primary electricity bill can be expressed in Equations (6) and (7). Because of the 100 kVA limit of the on-peak demand charge, the technical performance of the flexibility control can also be restricted by the operational cost. Because of this, a modified price calculation is proposed without a 100 kVA limit to investigate the further enhancement of the flexibility control as Table 3 displays. The modification would be as follows. (a) Demand Charge: During the on-peak period, the monthly maximum demand not exceeding 650 kVA would be charged at HKD 68.4/kVA, and there is no minimum on-peak billing demand. Meanwhile, there is no demand charge if the monthly maximum demand during the off-peak period is lower than during the on-peak period. If not, the power more than the on-peak demand is billed at HKD 26.8/kVA.Within the 20-year working period of the target building, the relative net present value (NPVrel) was employed to indicate the feasibility of the studies and facilitate comparisons among the research cases. Here, the relative net present value is based on the reference case, which is an all-grid case without renewable energy generation and no battery introduced to the system. Compared with the reference case, the additional battery cost and investment in renewables like the WEC and offshore wind turbine would be a capital expenditure (CAPEX). Operational expenditures (OPEX) include the operational and maintenance cost of the renewable devices, as well as the replacement cost of the battery, if applicable. The profit stems from saving on the electricity fee by flexibility control, the feed-in tariff, and the salvage value of the battery at the end of the twentieth year. The currency in the study is the Hong Kong dollar (HKD), with an exchange rate of HKD 7.77 to USD 1.00, according to the International Monetary Fund [46]. The NPVrel calculation is expressed in Equation (8), where the j is the working period often invariably from zero and i is the constant interest rate.This research is partially supported by the Project ID “P0033880” from Research Institute for Sustainable Urban Development (RISUD), and partially supported by the Project ID “P0039664” from Research Institute for Smart Energy (RISE), The Hong Kong Polytechnic University.
Publisher Copyright:
© 2022 Elsevier Ltd
PY - 2022/11/15
Y1 - 2022/11/15
N2 - Renewable resources are fluctuating and uncontrollable. The susceptible and intermittent generation not only causes the mismatch between the demand and supply but also brings grid pressure. Therefore, several measures were conducted on a coastal building energy system to enhance energy flexibility. From the aspects of operational cost, net present value, peak-shaving, valley-filling, and on-site electrical energy matching/fraction, a series of non-renewable and hybrid wave-wind-based renewable energy cases were studied to investigate the impact of the flexibility enhancement measures. Based on a specific electricity pricing scheme considering the monthly maximum power and the on-peak/off-peak energy demand, first, utilised the battery as a flexibility source to adjust the grid's interactions. It showed superior peak shaving capability during the on-peak period reaching 100%. Second, the battery control after the load which was partially covered by hybrid wind–wave energy reduced about 1% of operational cost. Generally, the battery control helped in various aspects whereas diminished the net present value due to high investment. Third, using the inherently integrated reservoir of the overtopping wave energy converter, the flexibility of the seawater discharging control like a reservoir-type power plant was investigated. The novel reservoir control presented outstanding comprehensive performance and feasibility. It enhanced the energy matching by 10% and reduced the operational cost to 83.99% compared with the case without employing control, bringing an extra 40% increment of relative net present value.
AB - Renewable resources are fluctuating and uncontrollable. The susceptible and intermittent generation not only causes the mismatch between the demand and supply but also brings grid pressure. Therefore, several measures were conducted on a coastal building energy system to enhance energy flexibility. From the aspects of operational cost, net present value, peak-shaving, valley-filling, and on-site electrical energy matching/fraction, a series of non-renewable and hybrid wave-wind-based renewable energy cases were studied to investigate the impact of the flexibility enhancement measures. Based on a specific electricity pricing scheme considering the monthly maximum power and the on-peak/off-peak energy demand, first, utilised the battery as a flexibility source to adjust the grid's interactions. It showed superior peak shaving capability during the on-peak period reaching 100%. Second, the battery control after the load which was partially covered by hybrid wind–wave energy reduced about 1% of operational cost. Generally, the battery control helped in various aspects whereas diminished the net present value due to high investment. Third, using the inherently integrated reservoir of the overtopping wave energy converter, the flexibility of the seawater discharging control like a reservoir-type power plant was investigated. The novel reservoir control presented outstanding comprehensive performance and feasibility. It enhanced the energy matching by 10% and reduced the operational cost to 83.99% compared with the case without employing control, bringing an extra 40% increment of relative net present value.
KW - Flexibility control
KW - Generation-side flexibility
KW - Hybrid renewable
KW - Peak shaving
KW - Wave energy converter
UR - http://www.scopus.com/inward/record.url?scp=85137267035&partnerID=8YFLogxK
U2 - 10.1016/j.jobe.2022.105167
DO - 10.1016/j.jobe.2022.105167
M3 - Journal article
AN - SCOPUS:85137267035
SN - 2352-7102
VL - 60
JO - Journal of Building Engineering
JF - Journal of Building Engineering
M1 - 105167
ER -