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  1. (R&D Dept. Kukje Electric Mfg. Co., Ltd., Korea. E-mail : david1973.lee@gmail.com)



Agricultural reservoirs, Floating solar power, Hybrid power system, Pumped-storage hydroelectricity, PV system, Grid stability

1. ์„œ ๋ก 

์˜จ์‹ค๊ฐ€์Šค ๊ฐ์ถ• ๋ฐ ํƒ„์†Œ ์ค‘๋ฆฝ ๋ชฉํ‘œ ๋‹ฌ์„ฑ์„ ์œ„ํ•ด ์ „ ์„ธ๊ณ„์ ์œผ๋กœ ์‹ ์žฌ์ƒ์—๋„ˆ์ง€์˜ ๊ฐœ๋ฐœ๊ณผ ํ™œ์šฉ์— ๋งŽ์€ ์—ฐ๊ตฌ ๋ฐ ์‹ค์ฆ์ด ํ™œ๋ฐœํ•˜๊ฒŒ ์ง„ํ–‰๋˜๊ณ  ์žˆ๋‹ค. ๋…๋ฆฝ๋œ ์—๋„ˆ์ง€์›์— ๋‹ค๋ฅธ ๋ฐœ์ „์„ค๋น„๋ฅผ ์ถ”๊ฐ€๋กœ ์ด์šฉํ•˜๋Š” ํ•˜์ด๋ธŒ๋ฆฌ๋“œ ๋ฐœ์ „์— ๊ด€ํ•œ ์—ฐ๊ตฌ ๋“ค์„ ์‚ดํŽด๋ณด๋ฉด, ์ธ๋„๋„ค์‹œ์•„์™€ ๋‚˜์ด์ง€๋ฆฌ์•„์˜ ์ „๋ ฅ ๋ฏธ๊ณต๊ธ‰ ์ง€์—ญ ๋Œ€์ƒ ํƒœ์–‘๊ด‘-์ˆ˜๋ ฅ ์ตœ์  ์„ค๊ณ„[1, 2, 3], ์ˆ˜์†Œ ์—๋„ˆ์ง€ ์—ฐ๊ณ„ ์‹œ์Šคํ…œ[4], ๋””์ ค ๋ฐœ์ „ ์˜์กด๋„๋ฅผ ๋‚ฎ์ถ”๋Š” ์†Œ์ˆ˜๋ ฅ-ํƒœ์–‘๊ด‘ ๊ฒฐํ•ฉ ๋ชจ๋ธ[5, 6, 7] ๋“ฑ์ด ๋ณด๊ณ ๋œ ๋ฐ” ์žˆ๋‹ค. ํŠนํžˆ ํŠน์ • ์‚ฐ์—… ์‹œ์„ค์ธ ์–‘์–ด์žฅ์—์„œ์˜ ์„ฑ๋Šฅ ํŒŒ๋ผ๋ฏธํ„ฐ๋ฅผ ๋ถ„์„ํ•˜์—ฌ ํšจ์œจ ์šด์ „์„ ์ œ๊ณ ํ•œ ์—ฐ๊ตฌ๋„ ์ง„ํ–‰๋˜์—ˆ๋‹ค[8].

์–‘์ˆ˜๋ฐœ์ „์€ ์ง€๊ธˆ๊นŒ์ง€ ์ฃผ๋กœ ๋Œ€์šฉ๋Ÿ‰ ์œ„์ฃผ๋กœ ๊ฐœ๋ฐœ๋˜์—ˆ์œผ๋‚˜, ์ƒˆ๋กœ์šด ์ž…์ง€ ํ™•๋ณด๊ฐ€ ์‰ฝ์ง€ ์•Š๊ณ  ํ™˜๊ฒฝ๋ฌธ์ œ ๋“ฑ์œผ๋กœ ์ธํ•ด ์‹ ๊ทœ ๊ฐœ๋ฐœ์— ๋งŽ์€ ์–ด๋ ค์›€์ด ๋”ฐ๋ฅธ๋‹ค. ๊ทธ๋Ÿฌ๋‚˜ ๋†์—…์šฉ ์ €์ˆ˜์ง€์™€ ๊ฐ™์€ ๊ณณ์€ ์šฉ๋Ÿ‰์€ ํฌ์ง€๋Š” ์•Š๋”๋ผ๋„, ํ•ญ์ƒ ๋†์—… ๊ด€๊ฐœ๋ฅผ ์œ„ํ•ด ํ•„์ˆ˜์ ์œผ๋กœ ๋ฌผ์„ ํ•ญ์‹œ ์ €์žฅํ•˜๋„๋ก ์ด๋ฏธ ์„ค์น˜๋œ ์‹œ์„ค์ด๋ฏ€๋กœ, ์‹ ๊ทœ ๊ฐœ๋ฐœ ๋น„์šฉ ๋ฐ ํ™˜๊ฒฝ๋ฌธ์ œ ์ธก๋ฉด์—์„œ ์ƒ๋Œ€์ ์œผ๋กœ ๋ถ€๋‹ด์ด ์ ๋‹ค.

์šฐ๋ฆฌ๋‚˜๋ผ๋Š” ๋†์—…์šฉ์œผ๋กœ ์ „๊ตญ์— ์•ฝ 17,147๊ฐœ์†Œ์˜ ์ €์ˆ˜์ง€๋ฅผ ๋ณด์œ ํ•˜๊ณ  ์žˆ์œผ๋ฉฐ[9], ์ด๋Š” ์‹ ๊ทœ ๊ฐœ๋ฐœ ์ด์šฉ ๋ฐ ํ™˜๊ฒฝ๋ฌธ์ œ ์ธก๋ฉด์—์„œ ์ƒ๋Œ€์ ์œผ๋กœ ๋ถ€๋‹ด์ด ์ ์€ ์—๋„ˆ์ง€ ์ž์›์ด๋‹ค.

๋ณธ ์—ฐ๊ตฌ๋Š” ๋†์—…์šฉ ์ €์ˆ˜์ง€์— ์„ค์น˜ ์šด์˜ ์ค‘์ธ ์†Œ์ˆ˜๋ ฅ ๋ฐœ์ „ ์„ค๋น„์— ์–‘์ˆ˜ ํŽŒํ•‘ ์„ค๋น„์™€ ์ˆ˜์ƒ ํƒœ์–‘๊ด‘์„ ๊ฒฐํ•ฉํ•œ ํ•˜์ด๋ธŒ๋ฆฌ๋“œ ๋ฐœ์ „ ๋ชจ๋ธ์„ ์ œ์•ˆํ•˜๊ณ , ๊ธฐ์ˆ ์  ํƒ€๋‹น์„ฑ ๋ฐ ๊ฒฝ์ œ์„ฑ ํšจ๊ณผ๋ฅผ ๋ถ„์„ํ•˜๊ณ ์ž ํ•œ๋‹ค.

2. ํ•˜์ด๋ธŒ๋ฆฌ๋“œ ๋ฐœ์ „ ์‹œ์Šคํ…œ ๋ฐ ๊ฒฝ์ œ์„ฑ ํ‰๊ฐ€

2.1 ํ•˜์ด๋ธŒ๋ฆฌ๋“œ ๋ฐœ์ „ ์‹œ์Šคํ…œ

ํ•˜์ด๋ธŒ๋ฆฌ๋“œ ๋ฐœ์ „ ์‹œ์Šคํ…œ(Hybrid Power System)์€ ๊ฐ„ํ—์„ฑ์ด ์žˆ๋Š” ์‹ ์žฌ์ƒ์—๋„ˆ์ง€๋ฅผ ์ฃผ๋ ฅ์œผ๋กœ ํ•˜๊ณ , ์—ฌ๊ธฐ์— ์•ˆ์ •์ ์ธ ์ €์žฅ ์žฅ์น˜(ESS)๋ฅผ ๊ฒฐํ•ฉํ•œ๋‹ค[10]. ๋ณธ ์‹œ์Šคํ…œ์€ ๊ณ ๊ฐ€์˜ ๋ฆฌํŠฌ ์ด์˜จ ๋ฐฐํ„ฐ๋ฆฌ(BESS)๋ฅผ ์„ค์น˜ํ•˜๋Š” ๋Œ€์‹ , ์ €์ˆ˜์ง€ ์ˆ˜์ฒด(Water body)๋ฅผ ์ƒ๋ถ€๋กœ ํŽŒํ•‘ํ•˜์—ฌ ์œ„์น˜ ์—๋„ˆ์ง€๋กœ ์ €์žฅํ•˜๋Š” ๊ธฐ๊ณ„์  ESS(Mechanical ESS) ๋ฐฉ์‹์„ ์ฑ„ํƒํ•œ๋‹ค.

ํƒœ์–‘๊ด‘ ๋ฐœ์ „์„ ๊ณ„ํ†ต๊ณผ ์ƒ์‹œ ์—ฐ๊ณ„๋˜๋ฉฐ, ํŽŒํ•‘ ์‹œ ํƒœ์–‘๊ด‘ ์ „๋ ฅ์„ ์šฐ์„  ์‚ฌ์šฉํ•˜๊ณ  ๋ถ€์กฑ ์‹œ ๊ณ„ํ†ต ์ „๋ ฅ์„ ์ˆ˜์ „ํ•˜์—ฌ ์–‘์ˆ˜ ์šด์ „์˜ ์—ฐ์†์„ฑ์„ ํ™•๋ณดํ•œ๋‹ค. ์ž‰์—ฌ์ „๋ ฅ์ด ๋ฐœ์ƒ ์‹œ์—๋Š” ์ด๋ฅผ ๊ณ„ํ†ต์— ํŒ๋งคํ•˜๋Š” ์œ ์—ฐํ•œ ๊ตฌ์กฐ๋ฅผ ๊ฐ€์ง„๋‹ค.

๊ทธ๋ฆผ 1์€ ํƒœ์–‘๊ด‘ ๋ฐœ์ „๊ณผ ์–‘์ˆ˜๋ฐœ์ „์ด ๊ฒฐํ•ฉ ๋œ ํ•˜์ด๋ธŒ๋ฆฌ๋“œ ๋ฐœ์ „์˜ ๊ฐœ๋…์„ ๋ณด์—ฌ์ค€๋‹ค. ํ˜„์žฌ ์ˆ˜๋ ฅ๋ฐœ์ „๋งŒ ์šด์˜ํ•˜๋Š” ๊ณณ์— ์–‘์ˆ˜๋ฐœ์ „์„ ๋„์ž…ํ•˜๊ณ  ์ˆ˜์ƒ ํƒœ์–‘๊ด‘ ๋ฐœ์ „์„ ์ ์šฉํ•˜๋ฉด, ํƒœ์–‘๊ด‘์˜ ์ž‰์—ฌ์ „๋ ฅ ํŽŒํ•‘์„ ์œ„ํ•œ ESS๋กœ ํ™œ์šฉํ•˜์—ฌ ๋ฌผ์„ ์–‘์ˆ˜ํ•œ ๋’ค, ์ „๋ ฅ ์‚ฌ์šฉ์ด ๋†’์€ ์‹œ๊ฐ„๋Œ€์— ๋ฐœ์ „ํ•จ์œผ๋กœ์จ ์œ ์šฉํ•˜๊ฒŒ ์ „๋ ฅ์„ ๊ณต๊ธ‰ํ•  ์ˆ˜ ์žˆ๋‹ค.

๊ทธ๋ฆผ 1. ํƒœ์–‘๊ด‘ ๋ฐœ์ „๊ณผ ์–‘์ˆ˜๋ฐœ์ „ ํ•˜์ด๋ธŒ๋ฆฌ๋“œ ์‹œ์Šคํ…œ์˜ ๊ฐœ๋…๋„

Fig 1. Conceptual diagram of a hybrid system combining solar power and pumped storage.

../../Resources/kiee/KIEE.2026.75.3.562/fig1.png

ํ•˜์ด๋ธŒ๋ฆฌ๋“œ ๋ฐœ์ „์„ ๋„์ž…ํ•˜๊ธฐ ์œ„ํ•ด์„œ๋Š” ๋Œ€์ƒ์ง€์˜ ์ ํ•ฉ์„ฑ์„ ๊ฒ€ํ† ํ•˜๊ณ , ์ตœ์ ์˜ ์„ค๋น„ ๊ตฌ์„ฑ์„ ๊ฒฐ์ •ํ•˜๋ฉฐ, ์ด์— ๋”ฐ๋ฅธ ์šฉ๋Ÿ‰์ด ํ•„์š”ํ•˜๋‹ค.

2.2 ์–‘์ˆ˜๋ฐœ์ „ ์‹œ์Šคํ…œ

์–‘์ˆ˜๋ฐœ์ „(Pumped-storage Hydroelectricity, PSH)์€ ๋ฐฐํ„ฐ๋ฆฌ ์—ญํ• ์„ ํ•˜๋Š” ๋ฐœ์ „ ๋ฐฉ์‹์œผ๋กœ, ์ „๋ ฅ ๊ณ„ํ†ต์˜ ์ž‰์—ฌ์ „๋ ฅ์„ ์ด์šฉํ•ด ๋ฌผ์„ ์ƒ๋ถ€ ์ €์ˆ˜์ง€์— ์ €์žฅํ–ˆ๋‹ค๊ฐ€ ํ•„์š”ํ•  ๋•Œ ๋ฐœ์ „ํ•˜์—ฌ ์ „๋ ฅ์„ ๊ณต๊ธ‰ํ•˜๋Š” ์—๋„ˆ์ง€ ์ €์žฅ ์žฅ์น˜(ESS)์˜ ํ•œ ์ข…๋ฅ˜์ด๋‹ค[10, 11, 12].

๋ฌผ์„ ์ƒ๋ถ€ ์ €์ˆ˜์ง€(Upper reservoir)๋กœ ํผ ์˜ฌ๋ฆฌ๊ฑฐ๋‚˜ ํ•˜๋ถ€ ์ €์ˆ˜์ง€๋กœ ๋–จ์–ด๋œจ๋ฆด ๋•Œ์˜ ์ด๋ก ์ ์ธ ์ตœ๋Œ€ ๋™๋ ฅ($P_{th}$)์€ ๋‹ค์Œ๊ณผ ๊ฐ™๋‹ค.

(1)
$P_{th} = \rho \times g \times Q \times H$

์—ฌ๊ธฐ์„œ, $\rho$์€ ๋ฌผ์˜ ๋ฐ€๋„์ด๊ณ , $g$์€ ์ค‘๋ ฅ๊ฐ€์†๋„์ด๋ฉฐ, $Q$๋Š” ์œ ๋Ÿ‰์ด๊ณ , $H$๋Š” ๋‚™์ฐจ์ด๋‹ค.

์–‘์ˆ˜๋ฐœ์ „์„ ์œ„ํ•ด ๋ฌผ์„ ํผ ์˜ฌ๋ฆด ๋•Œ ํ•„์š”ํ•œ ์ „๋™๊ธฐ์˜ ์šฉ๋Ÿ‰($P_{in}$)์€ ์ด๋ก  ๋™๋ ฅ์„ ํŽŒํ”„-์ „๋™๊ธฐ์˜ ์ด ํšจ์œจ๋กœ ๋‚˜๋ˆ„์–ด ๊ณ„์‚ฐํ•  ์ˆ˜ ์žˆ๋‹ค.

(2)
$P_{in} = \frac{P_{th}}{\eta_{total,pump}}$

์–‘์ˆ˜ํ•œ ๋ฌผ์„ ๋‹ค์‹œ ๋ฐฉ๋ฅ˜ํ•˜์—ฌ ๋ฐœ์ „ํ•  ๋•Œ ์˜ˆ์ƒ๋˜๋Š” ๋ฐœ์ „์ถœ๋ ฅ($P_{out}$)์€ ์ด๋ก  ์ถœ๋ ฅ์— ์ˆ˜์ฐจ-๋ฐœ์ „๊ธฐ ์ด ํšจ์œจ์„ ๊ณฑํ•˜์—ฌ ์‚ฐ์ถœํ•œ๋‹ค.

(3)
$P_{out} = P_{th} \times \eta_{total,turbine}$

์–‘์ˆ˜๋ฐœ์ „ ์‹œ์Šคํ…œ์˜ ์ค‘์š”ํ•œ ํŠน์„ฑ์ธ ์ˆœํ™˜ ํšจ์œจ(Round-trip Efficiency)์€ ์†Œ๋น„ํ•œ ์ „๋ ฅ ๋Œ€๋น„ ํšŒ์ˆ˜ํ•˜๋Š” ์ „๋ ฅ์˜ ๋น„์œจ๋กœ ๋‚˜ํƒ€๋‚ธ๋‹ค.

(4)
$\eta_{cycle} = \frac{P_{out}}{P_{in}}$

์–‘์ˆ˜๋ฐœ์ „ ์‹œ์Šคํ…œ์€ ์ „๋ ฅ ์ €์žฅ ๋ฐ ๊ณ„ํ†ต ์•ˆ์ •ํ™”์— ๋ชฉ์ ์ด ์žˆ์œผ๋ฏ€๋กœ, ์ด ์ˆœํ™˜ ํšจ์œจ์€ ์‹œ์Šคํ…œ์˜ ๊ฒฝ์ œ์„ฑ์„ ํŒ๋‹จํ•˜๋Š” ์ฃผ์š” ์ง€ํ‘œ๋กœ ํ™œ์šฉ๋œ๋‹ค.

2.3 ํƒœ์–‘๊ด‘ ๋ฐœ์ „ ์‹œ์Šคํ…œ

ํƒœ์–‘๊ด‘ ๋ฐœ์ „ ์‹œ์Šคํ…œ(Photovoltaic System, PV System)์€ ๋น› ์—๋„ˆ์ง€๋ฅผ ์ง์ ‘ ์ „๊ธฐ์—๋„ˆ์ง€๋กœ ์ง์ ‘ ๋ณ€ํ™˜ํ•˜๋Š” ์žฅ์น˜ ๋˜๋Š” ์„ค๋น„์˜ ์ง‘ํ•ฉ์ฒด๋กœ, ํ™”์„์—ฐ๋ฃŒ๋ฅผ ์‚ฌ์šฉํ•˜์ง€ ์•Š๋Š” ์นœํ™˜๊ฒฝ ์—๋„ˆ์ง€ ์ƒ์‚ฐ ์„ค๋น„์ด๋‹ค. ์ด ํƒœ์–‘๊ด‘ ์„ค๋น„๋ฅผ ์–‘์ˆ˜๋ฐœ์ „์— ์ ์šฉํ•  ๊ฒฝ์šฐ, ์„ค๋น„ ์šฉ๋Ÿ‰์€ ๋‹ค์Œ๊ณผ ๊ฐ™์€ ๋ฐฉ์‹์œผ๋กœ ๊ณ„์‚ฐํ•  ์ˆ˜ ์žˆ๋‹ค. ๋จผ์ € ์–‘์ˆ˜๋ฐœ์ „์„ ์œ„ํ•ด ํ•˜๋ถ€ ์ €์ˆ˜์กฐ(Lower reservoir) ์—์„œ ์ƒ๋ถ€ ์ €์ˆ˜์กฐ๋กœ ๋ฌผ์„ ํผ ์˜ฌ๋ฆด ๋•Œ ํ•„์š”ํ•œ ์ „๋ ฅ๋Ÿ‰($W_e$) ์„ ์‚ฐ์ •ํ•œ๋‹ค.

(5)
$W_e = \frac{\rho \times g \times Q \times H \times h}{\eta_{total,pump}} [kWh]$

์—ฌ๊ธฐ์„œ, $h$์€ ์–‘์ˆ˜ํ•  ๋•Œ ํ•„์š”ํ•œ ๊ฐ€๋™์‹œ๊ฐ„์ด๋‹ค. ํ•„์š”ํ•œ ํƒœ์–‘๊ด‘ ์„ค๋น„ ์šฉ๋Ÿ‰($kW_p$)์€ ํ•˜๋ฃจ ์ผ์กฐ ์‹œ๊ฐ„ ๋™์•ˆ ์ƒ๊ธฐ ์‹์—์„œ ์‚ฐ์ถœํ•œ ์–‘์ˆ˜ ์ˆ˜์š” ์—๋„ˆ์ง€๋ฅผ ์ƒ์‚ฐํ•  ์ˆ˜ ์žˆ๋„๋ก ์—ญ์‚ฐํ•˜์—ฌ ๊ตฌํ•  ์ˆ˜ ์žˆ๋‹ค.

(6)
$P_{PV} = \frac{W_e}{\text{์ผํ‰๊ท ํ”ผํฌ์ผ์กฐ์‹œ๊ฐ„}(h/day) \times pr} [kW_p]$

์—ฌ๊ธฐ์„œ $pr$์€ ๋ชจ๋“ˆ ํšจ์œจ, ์ธ๋ฒ„ํ„ฐ ํšจ์œจ, ๊ธฐํƒ€ ์†์‹ค ๊ณ„์ˆ˜ ๋“ฑ์„ ํฌํ•จํ•˜๋Š” ์‹œ์Šคํ…œ ํšจ์œจ์„ ๋‚˜ํƒ€๋‚ธ๋‹ค.

ํƒœ์–‘๊ด‘ ๋ฐœ์ „์„ค๋น„์˜ ์šฉ๋Ÿ‰์„ ๊ณ„์‚ฐํ•˜๊ธฐ ์œ„ํ•ด์„œ๋Š” ์šฐ์„  ๋ชจ๋“ˆ์˜ ์ •๊ฒฉ ์ถœ๋ ฅ($P_{max}$)์„ ์•Œ์•„์•ผ ํ•œ๋‹ค.

(7)
$P_{max} = V_{mpn} \times I_{mpn}$

์—ฌ๊ธฐ์„œ, $V_{mpn}$์€ ์ตœ๋Œ€ ์ „๋ ฅ ์ „์••, $I_{mpn}$์€ ์ตœ๋Œ€ ์ „๋ ฅ ์ „๋ฅ˜๋ฅผ ์˜๋ฏธํ•œ๋‹ค.

๋ฐœ์ „์— ํ•„์š”ํ•œ ๋ชจ๋“ˆ์˜ ์ด ๊ฐœ์ˆ˜($\text{module}_{ea}$)๋Š” ์„ค๋น„ ์šฉ๋Ÿ‰์„ ๋ชจ๋“ˆ ํ•˜๋‚˜์˜ ์šฉ๋Ÿ‰์œผ๋กœ ๋‚˜๋ˆ„์–ด ์‚ฐ์ถœํ•  ์ˆ˜ ์žˆ๋‹ค.

(8)
$\text{module}_{ea} = \frac{P_{PV}}{P_{max}}$

์‚ฐ์ถœ๋œ ๋ชจ๋“ˆ์˜ ์ด ๊ฐœ์ˆ˜๋Š” ์ €์ˆ˜์ง€์— ์„ค์น˜ํ•  ์ˆ˜ ์žˆ๋Š” ๊ณต๊ฐ„ ํ™•๋ณด ์—ฌ๋ถ€๋ฅผ ํŒ๋‹จํ•˜๋Š” ๋ฐ ํ™œ์šฉ๋œ๋‹ค.

2.4 ๊ฒฝ์ œ์„ฑ ํ‰๊ฐ€

๊ธฐ์กด ์„ค๋น„์— ์‹ ๊ทœ๋กœ ์„ค๋น„๋ฅผ ์ถ”๊ฐ€ํ•  ๊ฒฝ์šฐ, ๊ฒฝ์ œ์„ฑ ํ‰๊ฐ€๋Š” ์ˆœํ˜„์žฌ๊ฐ€์น˜์™€ ํŽธ์ต/๋น„์šฉ ๋น„์œจ(BCR, Benefit-Cost Ratio) ๋ถ„์„์„ ํ†ตํ•ด ์ง„ํ–‰๋œ๋‹ค. ์šฐ์„  ์ˆœํ˜„์žฌ๊ฐ€์น˜(NPV, Net Present Value)๋Š” ์‚ฌ์—…์œผ๋กœ ๋ฐœ์ƒํ•˜๋Š” ๋ชจ๋“  ๋ฏธ๋ž˜ ํ˜„๊ธˆ ํ๋ฆ„(ํŽธ์ต์—์„œ ๋น„์šฉ์„ ์ฐจ๊ฐ)์„ ํ˜„์žฌ ๊ฐ€์น˜๋กœ ํ• ์ธํ•˜์—ฌ ํ•ฉ์‚ฐํ•œ ๊ฐ’์œผ๋กœ, ์‹ (9)์™€ ๊ฐ™๋‹ค. ์ผ๋ฐ˜์ ์œผ๋กœ NPV๊ฐ€ 0๋ณด๋‹ค ํด ๊ฒฝ์šฐ, ํ•ด๋‹น ์‚ฌ์—…์€ ๊ฒฝ์ œ์  ํƒ€๋‹น์„ฑ์ด ์žˆ๋‹ค๊ณ  ํŒ๋‹จํ•œ๋‹ค.

(9)
$NPV = \sum_{t=1}^{n} \frac{(B_t - C_t)}{(1+r)^t}$

์—ฌ๊ธฐ์„œ, $n$ ์€ ๋ถ„์„ ๊ธฐ๊ฐ„, $r$์€ ํ• ์ธ์œจ, $t$๋Š” ์‹œ๊ฐ„ ๋‹จ์œ„๋กœ ๋ถ„์„ ๊ธฐ๊ฐ„ ๋‚ด ๊ฐ ์—ฐ๋„, $B_t$๋Š” ์—ฐ๊ฐ„ ํŽธ์ต, $C_t$๋Š” ์—ฐ๊ฐ„ ๋น„์šฉ($O_t$ ํฌํ•จ)์„ ๋‚˜ํƒ€๋‚ธ๋‹ค.

BCR ๋ถ„์„์„ ์ˆ˜ํ–‰ํ•˜๋Š” ์ฃผ๋œ ์ด์œ ๋Š” ํ•œ์ •๋œ ์ž์›์„ ๊ฐ€์žฅ ํšจ์œจ์ ์œผ๋กœ ํ™œ์šฉํ•˜์—ฌ ์ตœ๋Œ€์˜ ๊ฐ€์น˜์™€ ์ด์ต์„ ์ฐฝ์ถœํ•˜๋Š” ๋ฐ ์žˆ๋‹ค. BCR ์‚ฌ์—…์œผ๋กœ ๋ฐœ์ƒํ•˜๋Š” ํŽธ์ต์˜ ํ˜„์žฌ ๊ฐ€์น˜๋ฅผ ๋น„์šฉ์˜ ํ˜„์žฌ ๊ฐ€์น˜๋กœ ๋‚˜๋ˆˆ ๋น„์œจ์ด๋ฉฐ, ์‹ (10)๊ณผ ๊ฐ™๋‹ค.

(10)
$BCR = \frac{\sum_{t=1}^{n} \frac{B_t}{(1+r)^t}}{I_o + \sum_{t=1}^{n} \frac{O_t}{(1+r)^t}}$

์—ฌ๊ธฐ์„œ, $I_o$๋Š” ์ดˆ๊ธฐ ํˆฌ์ž ๋น„์šฉ์ด๊ณ , $O_t$๋Š” ์—ฐ๊ฐ„ ์šด์˜ ๋ฐ ์œ ์ง€๋ณด์ˆ˜ ๋น„์šฉ์„ ๋‚˜ํƒ€๋‚ธ๋‹ค. BCR์ด 1๋ณด๋‹ค ํด ๋•Œ ํ•ด๋‹นํ•˜๋Š” ์‚ฌ์—…์ด ๊ฒฝ์ œ์„ฑ์ด ์žˆ๋‹ค๊ณ  ํŒ๋‹จํ•œ๋‹ค.

3. ํ•ด์„ ๋ฐ ๊ฒฐ๊ณผ ๋ถ„์„

๋ณธ ์—ฐ๊ตฌ์—์„œ๋Š” ํ˜„์žฌ ์šด์˜ ์ค‘์ธ ์ €์ˆ˜์ง€๋ฅผ ๋Œ€์ƒ์œผ๋กœ ํƒœ์–‘๊ด‘ ๋ฐœ์ „์„ค๋น„์™€ ์–‘์ˆ˜ ์„ค๋น„ ๊ตฌ์ถ• ๋ฐ ์‹œ์Šคํ…œ ์„ค์น˜๋ฅผ ๊ฒ€ํ† ํ•˜์˜€๋‹ค. ํ•˜์ด๋ธŒ๋ฆฌ๋“œ ์šด์ „ ๋ถ„์„์„ ์œ„ํ•ด ์ ์šฉํ•œ ํ”„๋กœ๊ทธ๋žจ์€ ์ „์ž๊ณ„ ๊ณผ๋„ํ•ด์„ ํ”„๋กœ๊ทธ๋žจ(EMTP)์„ ํ™œ์šฉํ•˜์˜€๋‹ค[13].

ํ‘œ 1์€ ํ˜„์žฌ ๊ตญ๋‚ด์—์„œ ์šด์˜ ์ค‘์ธ ์ €์ˆ˜์ง€์˜ ์ฃผ์š” ์ œ์› ์ž๋ฃŒ๋ฅผ ๋ณด์—ฌ์ค€๋‹ค. ํ•ด๋‹น ์ €์ˆ˜์ง€์—์„œ๋Š” ์†Œ์ˆ˜๋ ฅ ๋ฐœ์ „์œผ๋กœ ์ „๋ ฅ์„ ์ƒ์‚ฐํ•˜์—ฌ ๊ณ„ํ†ต์— ๊ณต๊ธ‰ํ•˜๊ณ  ์žˆ์œผ๋ฉฐ, ํ‘œ 1์— ์ œ์‹œ๋œ ์œ ๋Ÿ‰๊ณผ ๋‚™์ฐจ๋ฅผ ํ†ตํ•ด ๋ฐœ์ „๊ธฐ์˜ ์ถœ๋ ฅ์„ ๊ณ„์‚ฐํ•  ์ˆ˜ ์žˆ๋‹ค.

ํ‘œ 1. ์ ์šฉํ•œ ์ €์ˆ˜์ง€์˜ ์ œ์›

Table 1. Specifications of applied reservoirs

์œ ์—ญ๋ฉด์  [ใŽข] ๊ด€๊ฐœ๋ฉด์  [ใŽข] ์œ ํšจ์ €์ˆ˜๋Ÿ‰ [์ฒœใŽฅ] ์œ ํšจ๋‚™์ฐจ [m] ๋ฐœ์ „ ์œ ๋Ÿ‰ [ใŽฅ/s]
218 57.13 30,301 9.57 4.0

ํƒœ์–‘๊ด‘ ๋ฐœ์ „ ์‹œ์Šคํ…œ ๊ตฌ์ถ•์— ํ•„์š”ํ•œ ๋ชจ๋“ˆ์˜ ์ถœ๋ ฅ๊ณผ ๊ฐœ์ˆ˜๋Š” ์„ ํƒํ•˜๋Š” ๋ชจ๋“ˆ์˜ ์ •๊ฒฉ ์ถœ๋ ฅ์— ๋”ฐ๋ผ ๋‹ฌ๋ผ์ง„๋‹ค. ๋ณธ ์—ฐ๊ตฌ์—์„œ๋Š” ์ตœ๊ทผ ์ƒ์—…์šฉ ํƒœ์–‘๊ด‘์œผ๋กœ ๋„๋ฆฌ ์‚ฌ์šฉ๋˜๋Š” 500Wp ์ œํ’ˆ์„ ์ ์šฉํ•˜์˜€๋‹ค. ์ด ๋ชจ๋“ˆ์˜ ์ฃผ์š” ํŒŒ๋ผ๋ฏธํ„ฐ๋Š” ํ‘œ 2์™€ ๊ฐ™๋‹ค.

ํ‘œ 2. ์ ์šฉํ•œ PV ๋ชจ๋“ˆ์˜ ์ œ์›

Table 2. Specifications of applied PV module

Items Values Remarks
$V_{mpn}$ 40.8V STC(Standard Test Condition)
$I_{mpn}$ 12A โ€œ
$P_{max}$ 489.6Wp 500W ์ ์šฉ

์œ„์˜ ์ €์ˆ˜์ง€ ์กฐ๊ฑด์„ ๊ณ ๋ คํ•˜์—ฌ ์–‘์ˆ˜๋ฐœ์ „๊ณผ ์–‘์ˆ˜ ์šฉ๋Ÿ‰ ๊ทธ๋ฆฌ๊ณ  ํƒœ์–‘๊ด‘ ๋ฐœ์ „์˜ ์šฉ๋Ÿ‰์„ ๊ตฌํ•˜๋ฉด ๋‹ค์Œ๊ณผ ๊ฐ™์ด ์–‘์ˆ˜๋ฐœ์ „์—์„œ ์ „๋™๊ธฐ ๋ชจ๋“œ ์šด์ „๊ณผ ๋ฐœ์ „๊ธฐ ๋ชจ๋“œ ์šด์ „ ์‹œ ์ „๋ ฅ ๊ทธ๋ฆฌ๊ณ  ํƒœ์–‘๊ด‘ ๋ฐœ์ „์—์„œ ํ•„์š”ํ•œ ์ „๋ ฅ์„ ๊ตฌํ•  ์ˆ˜ ์žˆ๋‹ค.

์•ž์„œ ์ œ์‹œํ•œ ์ €์ˆ˜์ง€ ์ œ์›๊ณผ ๋ชจ๋“ˆ ํŒŒ๋ผ๋ฏธํ„ฐ๋ฅผ ๋ฐ”ํƒ•์œผ๋กœ ์–‘์ˆ˜๋ฐœ์ „ ๋ฐ ํƒœ์–‘๊ด‘ ๋ฐœ์ „์„ค๋น„์˜ ์šฉ๋Ÿ‰์„ ์‚ฐ์ถœํ•œ ๊ฒฐ๊ณผ๋Š” ํ‘œ 3๊ณผ ๊ฐ™๋‹ค.

ํ‘œ 3. ์–‘์ˆ˜๋ฐœ์ „ ๋ฐ ํƒœ์–‘๊ด‘ ๋ฐœ์ „ ์‹œ ์ „๋ ฅ

Table 3. Power generation from hydroelectric and solar power plants

๊ตฌ๋ถ„ ๊ณ„์‚ฐ ๊ฒฐ๊ณผ ๋น„๊ณ 
์–‘์ˆ˜๋ฐœ์ „(๋ฐœ์ „ ์šฉ๋Ÿ‰) 319.2kW ๋ฐœ์ „ ํšจ์œจ 87% ์ ์šฉ
์–‘์ˆ˜๋ฐœ์ „(์–‘์ˆ˜ ์šฉ๋Ÿ‰) 426.7kW ํŽŒํ”„ ํšจ์œจ 88% ์ ์šฉ (์ „๋™๊ธฐ ์šฉ๋Ÿ‰)
ํ•„์š” ํƒœ์–‘๊ด‘ ์šฉ๋Ÿ‰ 533.4kWp 1์ผ 4์‹œ๊ฐ„ ์–‘์ˆ˜

ํ‘œ 3์€ ๋‚™์ฐจ 9.57m, ์œ ๋Ÿ‰ 4.0ใŽฅ/s ์กฐ๊ฑด์„ ๋ฐ”ํƒ•์œผ๋กœ ๋ถ„์„ํ•œ ๊ฒฐ๊ณผ, ์–‘์ˆ˜๋ฐœ์ „ ์šฉ๋Ÿ‰์€ 319.2kW, ํŽŒํ•‘์šฉ ์ „๋™๊ธฐ ์šฉ๋Ÿ‰ 426.7kW๋กœ ์‚ฐ์ •๋˜์—ˆ๋‹ค. ์ด๋ฅผ ์œ„ํ•ด ํ•„์š”ํ•œ ์ตœ์†Œ ํƒœ์–‘๊ด‘ ์šฉ๋Ÿ‰์€ 533.4$kW_p$์ด๋ฉฐ, ์„ค์น˜ ๋ฉด์ ์€ ์ €์ˆ˜์ง€ ๊ด€๊ฐœ๋ฉด์  ๋Œ€๋น„ ์•ฝ 4.7%์ธ 2,680ใŽก๋กœ ์‚ฐ์ถœ๋˜์—ˆ๋‹ค. ํ‘œ 3์—์„œ ์–‘์ˆ˜ ์‹œ์˜ ์šฉ๋Ÿ‰(์ „๋™๊ธฐ ์šฉ๋Ÿ‰)์ด ๋ฐœ์ „ ์‹œ ์–ป๋Š” ์šฉ๋Ÿ‰๋ณด๋‹ค ๋” ๋†’์€ ์ด์œ ๋Š” ์‹œ์Šคํ…œ์˜ ์ˆœํ™˜ ํšจ์œจ ๋•Œ๋ฌธ์ด๋‹ค.

๋‹ค์Œ์œผ๋กœ, ์–‘์ˆ˜๋ฐœ์ „์— ํƒœ์–‘๊ด‘ ๋ฐœ์ „์„ค๋น„๋ฅผ ๋„์ž…ํ–ˆ์„ ๋•Œ์˜ ์ „๋ ฅ ๋ณ€ํ™”๋ฅผ ํ™•์ธํ•˜๊ธฐ ์œ„ํ•ด ์ „์ž๊ณ„ ๊ณผ๋„ํ•ด์„ ํ”„๋กœ๊ทธ๋žจ์„ ์ด์šฉํ•˜์—ฌ ๋ถ„์„ํ•˜์˜€๋‹ค[13]. EMTP์˜ Models ์–ธ์–ด๋ฅผ ์ด์šฉํ•˜์—ฌ ๊ตฌํ˜„๋œ MPPT(Maximum Power Point Tracking) ์ œ์–ด ๋ธ”๋ก๋„๋Š” ๊ทธ๋ฆผ 2์™€ ๊ฐ™๋‹ค.

๊ทธ๋ฆผ 2. MPPT ์ œ์–ด ์•Œ๊ณ ๋ฆฌ์ฆ˜

Fig 2. MPPT control algorithm

../../Resources/kiee/KIEE.2026.75.3.562/fig2.png

๊ทธ๋ฆผ 2์˜ ์ œ์–ด ์•Œ๊ณ ๋ฆฌ์ฆ˜์€ ์‹œ๋ฎฌ๋ ˆ์ด์…˜ ํƒ€์ž„ ์Šคํ…(step) ๋งˆ๋‹ค ๋ฐ˜๋ณต ์‹คํ–‰๋œ๋‹ค. ์ด ์•Œ๊ณ ๋ฆฌ์ฆ˜์€ PV ์ „๋ ฅ ์ธก์ •, MPPT ๋กœ์ง ์ˆ˜ํ–‰, ๊ณ„ํ†ต ์œ„์ƒ ๋™๊ธฐํ™”(PLL) ๊ณผ์ •์„ ๊ฑฐ์ณ ์ธ๋ฒ„ํ„ฐ ์ „๋ฅ˜๋ฅผ ์ถœ๋ ฅํ•˜๋ฉฐ, ๊ณ„ํ†ต์— ์•ˆ์ •์ ์œผ๋กœ ์ „๋ ฅ์„ ์ œ๊ณตํ•˜๋„๋ก ๋™์ž‘ํ•œ๋‹ค.

๋ณธ ์—ฐ๊ตฌ๋Š” ์†Œ์ˆ˜๋ ฅ ๋ฐœ์ „๋งŒ ์šด์ „ ์ค‘์ธ ์ €์ˆ˜์ง€์— ์–‘์ˆ˜๋ฐœ์ „์„ ๋„์ž…ํ•˜๊ณ , ํŽŒํ•‘์— ํ•„์š”ํ•œ ์ „๋ ฅ์„ ์ˆ˜์ƒ ํƒœ์–‘๊ด‘ ์„ค๋น„๋กœ ๋Œ€์ฒดํ•˜๋Š” ํ•˜์ด๋ธŒ๋ฆฌ๋“œ ๋ฐœ์ „ ์‹œ์Šคํ…œ์„ ๊ตฌ์ƒํ•˜์˜€๋‹ค. ์ด์— ๋”ฐ๋ผ, ํƒœ์–‘๊ด‘ ๋ฐœ์ „์ด ๊ฐ€๋Šฅํ•œ ์‹œ๊ฐ„๋Œ€์—๋Š” ํƒœ์–‘๊ด‘ ๋ฐœ์ „๊ณผ ์–‘์ˆ˜๋ฐœ์ „์„ ๋ณ‘ํ–‰ํ•˜๊ณ , ํƒœ์–‘๊ด‘ ๋ฐœ์ „์ด ์–ด๋ ค์šด ์‹œ๊ฐ„๋Œ€์—๋Š” ์ˆ˜๋ ฅ๋ฐœ์ „๋งŒ์œผ๋กœ ์ „๋ ฅ์„ ์ƒ์‚ฐํ•˜๋„๋ก ์‹œ์Šคํ…œ์„ ์„ค์ •ํ•˜์˜€๋‹ค.

๊ทธ๋ฆผ 3์€ ๊ธฐ์กด์— ๋ฐœ์ „ ์šด์˜ ์˜์—ญ(โ‘ , โ‘ข์˜์—ญ)์— ์–‘์ˆ˜๋ฐœ์ „์„ ์œ„ํ•ด ํŽŒํ•‘ ๋™์ž‘(โ‘ก ์˜์—ญ)์„ ๋„์ž…ํ–ˆ์„ ๋•Œ์˜ ์ „๋ ฅ ๋ณ€ํ™”๋ฅผ ๋‚˜ํƒ€๋‚ธ๋‹ค. ๋ฐœ์ „๊ณผ ํŽŒํ•‘ ๋™์ž‘ ์‹œ ์ „๋ ฅ ๋ฐฉํ–ฅ์€ ์„œ๋กœ ๋ฐ˜๋Œ€์ด๋ฉฐ, ์ด ๋™์ž‘์—์„œ ์ „๊ธฐ์  ์ถœ๋ ฅ(โ—‹)๊ณผ ๊ธฐ๊ณ„์  ์ถœ๋ ฅ(โ–ก)์„ ๋น„๊ตํ•˜์˜€๋‹ค.

๋ฐœ์ „๊ธฐ๋กœ ์šด์ „ ์ƒํƒœ(โ‘ , โ‘ข์˜์—ญ)์—์„œ ๊ณ„ํ†ต์œผ๋กœ ๊ณต๊ธ‰๋˜๋Š” ์œ ํšจ์ „๋ ฅ(โ—‹)์€ ํ‘œ 3์˜ ๊ณ„์‚ฐ ๊ฒฐ๊ณผ์™€ ์ผ์น˜ํ•œ๋‹ค. ์ด๋•Œ ๊ธฐ๊ณ„์ ์ธ ์ž…๋ ฅ์€ 366.97kW์ด๋ฉฐ, ํšจ์œจ์€ ์•ฝ 87%์ด๋‹ค. ์ƒ๋ถ€ ์ €์ˆ˜์กฐ๋กœ ๋ฌผ์„ ํผ ์˜ฌ๋ฆฌ๋Š” ์ „๋™๊ธฐ ์šด์ „ ์˜์—ญ(โ‘ก ์˜์—ญ)์—์„œ ํ•„์š”ํ•œ ์œ ํšจ์ „๋ ฅ(โ—‹)์€ 426.5kW์ด๋ฉฐ, ์ด ์ „๋ ฅ์€ ์™ธ๋ถ€ ์ „์›์œผ๋กœ๋ถ€ํ„ฐ ๊ณต๊ธ‰๋˜์–ด์•ผ ํ•œ๋‹ค.

๊ทธ๋ฆผ 3. ์–‘์ˆ˜๋ฐœ์ „ ์‹œ ์ „๋ ฅ

Fig 3. Power generation during pumped storage

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๊ทธ๋ฆผ 3๊ณผ ๊ฐ™์€ ์–‘์ˆ˜๋ฐœ์ „ ์šด์ „์—์„œ ํƒœ์–‘๊ด‘ ๋ฐœ์ „์„ ์ ์šฉํ•˜๋Š” ์˜์—ญ์€ ํŽŒํ•‘ ๋™์ž‘ ์‹œ์ด๋ฉฐ, ์ด๋•Œ ํƒœ์–‘๊ด‘์œผ๋กœ ์ƒ์‚ฐ๋œ ์ „๋ ฅ์„ ํŽŒํ•‘์— ์‚ฌ์šฉํ•œ๋‹ค. ํƒœ์–‘๊ด‘ ๋ฐœ์ „๋Ÿ‰์ด ๊ธ‰๋ณ€ํ•˜๋”๋ผ๋„ ์ „๋ ฅ์„ ์ผ์ •ํ•˜๊ฒŒ ์–ป๊ธฐ ์œ„ํ•ด MPPT ์ œ์–ด ๊ธฐ๋ฒ•์„ ์ ์šฉํ•˜์˜€์œผ๋ฉฐ, ์‹œ๋ฎฌ๋ ˆ์ด์…˜ ์กฐ๊ฑด์œผ๋กœ ๋‹จ์œ„ ๋ฉด์ ๋‹น ์ผ์‚ฌ๋Ÿ‰์€ 1000W, ๋ชจ๋“ˆ ์˜จ๋„๋Š” 45โ„ƒ๋กœ ์„ค์ •ํ•˜์˜€๋‹ค.

๊ทธ๋ฆผ 4๋Š” ์–‘์ˆ˜๋ฐœ์ „์— ์ˆ˜์ƒ ํƒœ์–‘๊ด‘ ๋ฐœ์ „์„ ๊ฒฐํ•ฉํ–ˆ์„ ๋•Œ์˜ ์ „๋ ฅ ๋ณ€ํ™”๋ฅผ ๋ณด์—ฌ์ค€๋‹ค. โ‘ ๊ณผ โ‘ข์˜์—ญ์€ ๊ธฐ์กด๊ณผ ๊ฐ™๊ฒŒ ์ €์ˆ˜์ง€ ๋ฌผ์„ ์ด์šฉํ•ด ๋ฐœ์ „ํ•  ๋•Œ์˜ ์ „๋ ฅ(โ–ก)์„ ๋‚˜ํƒ€๋‚ด๋ฉฐ, ์ด๋•Œ๋Š” ํƒœ์–‘๊ด‘ ๋ฐœ์ „์„ ์šด์ „ํ•˜์ง€ ์•Š์•˜๋‹ค. โ‘ก์˜์—ญ์€ ํŽŒํ•‘์ด ํ•„์š”ํ•œ ๊ตฌ๊ฐ„์—์„œ ํƒœ์–‘๊ด‘ ๋ฐœ์ „์„ ์šด์ „ํ•˜์—ฌ ์ƒ์‚ฐ๋œ ์ „๋ ฅ(โ—ฏ)์„ ๋ณด์—ฌ์ค€๋‹ค. ํƒœ์–‘๊ด‘ ๋ฐœ์ „์œผ๋กœ ์–ป์€ ์ „๋ ฅ์€ ํŽŒํ•‘์— ํ•„์š”ํ•œ ์ „๋ ฅ๋ณด๋‹ค ๋†’์•„์•ผ ํ•œ๋‹ค. ์‹œ๋ฎฌ๋ ˆ์ด์…˜ ๊ฒฐ๊ณผ, ํƒœ์–‘๊ด‘ ์ „๋ ฅ์œผ๋กœ ์–ป์€ 443kW๋กœ ํŽŒํ•‘์— ํ•„์š”ํ•œ ์ „๋ ฅ(426.7kW)๋ณด๋‹ค ์•ฝ๊ฐ„ ๋†’์€ ์ˆ˜์ค€์ด๋‹ค. ์ด๋Š” ํ•„์š”ํ•œ ํƒœ์–‘๊ด‘ ๋ฐœ์ „์„ค๋น„ ์šฉ๋Ÿ‰์ด ํ•˜๋ฃจ 4์‹œ๊ฐ„ ์–‘์ˆ˜ ์ˆ˜์š” ์—๋„ˆ์ง€ ๊ณต๊ธ‰์„ ๊ณ ๋ คํ•˜์—ฌ ์„ค๊ณ„๋˜์—ˆ๊ธฐ ๋•Œ๋ฌธ์ด๋ฉฐ, ํ•˜์ด๋ธŒ๋ฆฌ๋“œ ์šด์ „ ์‹œ ํƒœ์–‘๊ด‘ ๋ฐœ์ „๋Ÿ‰์ด ํŽŒํ•‘ ์ˆ˜์š”๋ฅผ ์ถฉ์กฑ์‹œํ‚ฌ ์ˆ˜ ์žˆ์Œ์„ ์˜๋ฏธํ•œ๋‹ค.

๊ทธ๋ฆผ 4. ํ•˜์ด๋ธŒ๋ฆฌ๋“œ ์šด์ „ ์‹œ ์ „๋ ฅ์˜ ๋ณ€ํ™”

Fig 4. Changes in power during hybrid driving

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๊ทธ๋ฆผ 3๊ณผ ๊ทธ๋ฆผ 4์—์„œ ๋ถ„์„๋œ ์–‘์ˆ˜๋ฐœ์ „ ์‹œ ๋น„์ž‘๋™ ์‹œ์˜ ์ „๋ ฅ๊ฐ’์€ ํ‘œ 3์˜ ๊ณ„์‚ฐ ๊ฒฐ๊ณผ์™€ ๊ฑฐ์˜ ์ผ์น˜ํ•จ์„ ํ™•์ธํ•˜์˜€๋‹ค.

๊ทธ๋ฆผ 5๋Š” ๊ธฐ์กด ์ˆ˜๋ ฅ๋ฐœ์ „(Generating)์— ์–‘์ˆ˜๋ฐœ์ „(Pumping) ๋ฐ ํƒœ์–‘๊ด‘ ๋ฐœ์ „(PV Generating)์„ ์—ฐ๊ณ„ํ•œ ํ•˜์ด๋ธŒ๋ฆฌ๋“œ ์šด์ „ ์‹œ ๊ณ„ํ†ต ์ฃผํŒŒ์ˆ˜ ๋ณ€ํ™”๋ฅผ ๋ณด์—ฌ์ค€๋‹ค. ํƒœ์–‘๊ด‘ ๋ฐœ์ „๋Ÿ‰ ๊ธ‰๋ณ€ ์กฐ๊ฑด์—์„œ๋„ ์•ˆ์ •์ ์ธ ์ „๋ ฅ๊ณต๊ธ‰์„ ์œ„ํ•ด MPPT ์ œ์–ด ์•Œ๊ณ ๋ฆฌ์ฆ˜์„ ์ ์šฉํ•˜์—ฌ ๊ณผ๋„ ํ•ด์„ ํ”„๋กœ๊ทธ๋žจ์œผ๋กœ ๋ถ„์„ํ•˜์˜€๋‹ค. ํ•ด์„ ๊ฒฐ๊ณผ, ํ•˜์ด๋ธŒ๋ฆฌ๋“œ ์šด์ „ ์‹œ ๊ณ„ํ†ต ์ฃผํŒŒ์ˆ˜๊ฐ€ ํ•ญ์ƒ 60ใސ๋กœ ์ผ์ •ํ•˜๊ฒŒ ์œ ์ง€๋˜๋Š” ๊ฒƒ์„ ํ™•์ธํ•˜์˜€๋‹ค. ์ด๋Š” ์–‘์ˆ˜๋ฐœ์ „(PSH) ์‹œ์Šคํ…œ์ด ESS ๊ธฐ๋Šฅ์„ ์ˆ˜ํ–‰ํ•˜์—ฌ ์ˆ˜์ƒ ํƒœ์–‘๊ด‘์˜ ๊ฐ„ํ—์ ์ธ ๋ฐœ์ „ ํŠน์„ฑ์„ ํšจ๊ณผ์ ์œผ๋กœ ๋ณด์™„ํ•จ์œผ๋กœ์จ, ๊ณ„ํ†ต ์—ฐ๊ณ„ ์šด์ „์˜ ์•ˆ์ •์„ฑ์ด ๋ณด์žฅ๋จ์„ ์‹œ์‚ฌํ•œ๋‹ค.

๊ทธ๋ฆผ 5. ํ•˜์ด๋ธŒ๋ฆฌ๋“œ ์šด์ „ ์‹œ ์ฃผํŒŒ์ˆ˜์˜ ๋ณ€ํ™”

Fig 5. Frequency changes during hybrid driving

../../Resources/kiee/KIEE.2026.75.3.562/fig5.png

๋‹ค์Œ์€ ๊ธฐ์กด ์ €์ˆ˜์ง€์— ์–‘์ˆ˜๋ฐœ์ „๊ณผ ํƒœ์–‘๊ด‘ ๋ฐœ์ „ ์„ค๋น„๋ฅผ ํ•จ๊ป˜ ๊ตฌ์ถ•ํ•œ ํ•˜์ด๋ธŒ๋ฆฌ๋“œ ์‹œ์Šคํ…œ ๋„์ž… ๋ฐ ์šด์˜์— ๋Œ€ํ•œ ๊ฒฝ์ œ์„ฑ ๋ถ„์„์„ ์ˆ˜ํ–‰ํ•œ๋‹ค. ๊ฒฝ์ œ์„ฑ ํ‰๊ฐ€๋ฅผ ์œ„ํ•ด ์„ค๋น„์˜ ํˆฌ์ž๋น„, ์šด์˜๋น„, ํŽธ์ต ๋ฐ ์ด์šฉ๋ฅ  ๋“ฑ ๊ฐ๊ด€์ ์ธ ์ž๋ฃŒ๋Š” ๊ตญ๋‚ด์—์„œ ํ˜„์žฌ ์‚ฌ์šฉ๋˜๋Š” ๊ฐ’์„ ์ ์šฉํ•˜์˜€์œผ๋ฉฐ, ์ด๋Š” ํ‘œ 4์™€ ๊ฐ™๋‹ค.

ํ‘œ 4. ๊ฒฝ์ œ์„ฑ ํ‰๊ฐ€๋ฅผ ์œ„ํ•œ ๊ณ„์‚ฐ ์กฐ๊ฑด

Table 4. Accounting conditions for economic evaluation

๊ตฌ๋ถ„ ํ•ญ๋ชฉ ๊ฐ€์ •์น˜ ์ ์šฉ ๊ทผ๊ฑฐ
๊ธฐ๊ฐ„ ๋ถ„์„ ๊ธฐ๊ฐ„ (n) 20๋…„ ํƒœ์–‘๊ด‘ ๋ฐœ์ „์„ค๋น„์˜ ์ผ๋ฐ˜์ ์ธ ๋‚ด๊ตฌ์—ฐํ•œ
์ดˆ๊ธฐ ํˆฌ์ž ์—ฐ๋„ 0๋…„์ฐจ
์žฌ๋ฌด ํ• ์ธ์œจ (r) 5.50% ํ•œ๊ตญ ๊ณต๊ณต์‚ฌ์—… ์˜ˆ๋น„ํƒ€๋‹น์„ฑ์กฐ์‚ฌ์˜ ์‹ค์งˆ ํ• ์ธ์œจ ์ฐธ๊ณ 
๋ฌผ๊ฐ€์ƒ์Šน๋ฅ  (์‹ค์งˆ ๋ถ„์„ ๊ฐ€์ •) 0% ํŽธ์˜์ƒ ์‹ค์งˆ ๊ฐ€์น˜๋กœ ๋ถ„์„ํ•˜๋ฉฐ, ๋ช…๋ชฉ ๋ถ„์„ ์‹œ์—๋Š” ๋ฌผ๊ฐ€์ƒ์Šน๋ฅ ์„ ๋ฐ˜์˜ํ•จ
ํˆฌ์ž๋น„ ์–‘์ˆ˜ ์„ค๋น„ (ํŽŒํ”„/์ „๋™๊ธฐ) ์„ค์น˜ ๋‹จ๊ฐ€ 800๋งŒ ์›/kW ์†Œ๊ทœ๋ชจ ์–‘์ˆ˜๋ฐœ์ „ ์„ค๋น„์˜ ์ถ”์ • ๋‹จ๊ฐ€
ํƒœ์–‘๊ด‘ ์„ค๋น„ (์ˆ˜์ƒํ˜•) ์„ค์น˜ ๋‹จ๊ฐ€ 200๋งŒ ์›/kW ์ตœ๊ทผ ์ˆ˜์ƒ ํƒœ์–‘๊ด‘ ์„ค๋น„์˜ ์ถ”์ • ๋‹จ๊ฐ€
์šด์˜๋น„ ์—ฐ๊ฐ„ ์šด์˜ ๋ฐ ์œ ์ง€๋ณด์ˆ˜ (O&M) ๋น„์šฉ ์ดˆ๊ธฐ ํˆฌ์ž๋น„์˜ 1% ์ผ๋ฐ˜์ ์ธ ๋ฐœ์ „์†Œ O&M ๋น„์œจ ์ฐธ๊ณ 
ํŽธ์ต ๊ณ„ํ†ตํ•œ๊ณ„๊ฐ€๊ฒฉ (SMP) 150์› /kWh ์ „๋ ฅ ๋„๋งค์‹œ์žฅ ๊ฐ€๊ฒฉ ๋ณ€๋™์„ฑ์„ ๊ณ ๋ คํ•œ ์˜ˆ์‹œ ํ‰๊ท  ๋‹จ๊ฐ€
REC ํ‰๊ท  ๊ฑฐ๋ž˜ ๊ฐ€๊ฒฉ (๊ฐ€์ค‘์น˜ ํฌํ•จ) 90์› /kWh REC ๊ฐ€๊ฒฉ ๋ณ€๋™์„ฑ์„ ๊ณ ๋ คํ•œ ์˜ˆ์‹œ ํ‰๊ท  ๋‹จ๊ฐ€
์ด์šฉ๋ฅ  ํƒœ์–‘๊ด‘ ์„ค๋น„ ์ด์šฉ๋ฅ  15% ํ•œ๊ตญ ์ˆ˜์ƒ ํƒœ์–‘๊ด‘์˜ ์ผ๋ฐ˜์ ์ธ ์ด์šฉ๋ฅ  ์ฐธ๊ณ 

ํ‘œ 5. ์ˆœํ˜„์žฌ๊ฐ€์น˜ ๋ฐ ํŽธ์ต/๋น„์šฉ์˜ ๊ณ„์‚ฐ ๊ฒฐ๊ณผ

Table 5. Calculation results of net present value and benefits/costs

Items Values Remarks
$I_o$ ์–‘์ˆ˜ ์„ค๋น„ ํˆฌ์ž ๋น„์šฉ 426.7kWร—8๋ฐฑ๋งŒ์›/kW=3,413๋ฐฑ๋งŒ์›
ํƒœ์–‘๊ด‘ ์„ค๋น„ ํˆฌ์ž ๋น„์šฉ 533kWร—2๋ฐฑ๋งŒ์›/kW=1,066.8๋ฐฑ๋งŒ์›
์ด ๋น„์šฉ 4,480.4๋ฐฑ๋งŒ์›
$B_t$ ์–‘์ˆ˜๋ฐœ์ „ ์—ฐ๊ฐ„ ๋ฐœ์ „๋Ÿ‰ 319.2kWร—1,116h/y =356,000kWh/y ํŽŒํ•‘ ์‹œ๊ฐ„ 4h/day ์ˆœํ™˜ ํšจ์œจ 76.5%
ํƒœ์–‘๊ด‘ ์—ฐ๊ฐ„ ๋ฐœ์ „๋Ÿ‰ 533.4kWร—8,760h/yร—15% = 700,900kWh
์ดํŒ๋งค ์ˆ˜์ต 356,000kWhร—150์› /kWh=53.4๋ฐฑ๋งŒ์›(์–‘์ˆ˜)+ 700,900kWhร—240์› /kWh=168.2๋ฐฑ๋งŒ์›(ํƒœ์–‘๊ด‘) =221.6๋ฐฑ๋งŒ์› ์–‘์ˆ˜๋ฐœ์ „์€ SMP๋งŒ ์ ์šฉ, ํƒœ์–‘๊ด‘์€ SMP+REC ์ ์šฉ
์šด์˜๋น„ ์ ˆ๊ฐ์•ก (ํŽŒํ•‘ ์ „๋ ฅ ์ž๊ฐ€ ์†Œ๋น„) ์–‘์ˆ˜ ์šด์ „ ํ•„์š” ์ „๋ ฅ๋Ÿ‰ 426.7kWร—4h/dร—365d =623,700kWhร—100์›/kWh =62.4๋ฐฑ๋งŒ์› ํŽŒํ•‘ ์ „๋ ฅ ๊ตฌ๋งค ๋‹จ๊ฐ€ : 100์›/kWh
$B_t$ 284.0๋ฐฑ๋งŒ์›/y ํŒ๋งค ์ˆ˜์ต+์šด์˜๋น„ ์ ˆ๊ฐ
$O_t$ $I_o$ร—1%=44.8๋ฐฑ๋งŒ์›/y O&M ๋น„์œจ 1%
NPV $NPV = (B_t - C_t) \times PVIFA = 2,858.44 - 4,480.4 = -1,621.96$๋ฐฑ๋งŒ์› ํ• ์ธ์œจ 5.5%, ๋ถ„์„ ๊ธฐ๊ฐ„ 20๋…„ ์—ฐ๊ธˆ ํ˜„๊ฐ€๊ณ„์ˆ˜(PVIFA) 11.95%
BCR ํŽธ์ต ํ˜„์žฌ ๊ฐ€์น˜ : $B_t \times PVIFA = 3,394.6$๋ฐฑ๋งŒ ๋น„์šฉ์˜ ํ˜„์žฌ ๊ฐ€์น˜ : $O_t + O.M \times PVIFA = 5,015.6$๋ฐฑ๋งŒ์› $BCR = 0.68$

ํ‘œ 4์˜ ๊ณ„์‚ฐ ์กฐ๊ฑด์„ ์ ์šฉํ•œ ์ดˆ๊ธฐ ๋ชจ๋ธ(PV 533.4kW)์˜ BCR์€ 0.68๋กœ ๊ฒฝ์ œ์„ฑ์ด ๋‚ฎ๊ฒŒ ํ‰๊ฐ€๋˜์—ˆ๋‹ค. ์ด์— ๋Œ€ํ•œ ๋Œ€์•ˆ์œผ๋กœ ํƒœ์–‘๊ด‘ ์šฉ๋Ÿ‰์„ 4๋ฐฐ๋กœ ํ™•์žฅํ•˜๋Š” ์ตœ์ ํ™” ๋ชจ๋ธ์„ ๊ฒ€ํ† ํ•˜์˜€์œผ๋ฉฐ, ์ด ๊ฒฝ์šฐ BCR์ด 1.1๋กœ ์ƒ์Šนํ•จ์„ ํ™•์ธํ•˜์˜€๋‹ค. ์ด์— ๋Œ€ํ•œ ๊ฐœ๋žต์ ์ธ ๊ทผ๊ฑฐ๋Š” ๋‹ค์Œ๊ณผ ๊ฐ™๋‹ค.

โ‘  ๊ทœ๋ชจ์˜ ๊ฒฝ์ œ : ๊ณ ์ •๋น„ ์„ฑ๊ฒฉ์ด ๊ฐ•ํ•œ ์–‘์ˆ˜ ์„ค๋น„์— ๋น„ํ•ด ์ˆ˜์ƒ ํƒœ์–‘๊ด‘์˜ ์ถ”๊ฐ€ ์„ค์น˜ ๋‹จ๊ฐ€๊ฐ€ ์ €๋ ดํ•˜์—ฌ ๋‹จ์œ„๋‹น ๊ฑด์„ค ๋น„์šฉ์ด ํ•˜๋ฝํ•œ๋‹ค.

โ‘ก ์‹œ์„ค๋น„ ์ตœ์†Œํ™” : ์šฉ๋Ÿ‰ ํ™•์žฅ ์‹œ์—๋„ ์ˆ˜๋ฉด ์ ์œ ์œจ์€ 18.8% ์ˆ˜์ค€์œผ๋กœ, ์ถ”๊ฐ€ ํ† ๋ชฉ ๊ณต์‚ฌ ์—†์ด ๊ธฐ์กด ๊ตฌ์กฐ๋ฌผ์˜ ํ™•์žฅ๋งŒ์œผ๋กœ ๊ฐ€๋Šฅํ•˜๋‹ค.

โ‘ข ESS ๋น„์šฉ ์ ˆ๊ฐ : ์ˆ˜์ฒด๋ฅผ ์ง์ ‘ ์ €์žฅ ๋งค์ฒด๋กœ ํ™œ์šฉํ•˜๋ฏ€๋กœ PV ์ฆ์„ค์— ๋”ฐ๋ฅธ BESS ํ™•์ถฉ ๋น„์šฉ์ด ์ˆ˜๋ฐ˜๋˜์ง€ ์•Š์œผ๋ฉฐ, ํŒ๋งค ์ˆ˜์ต(SMP+REC)์ด ์ง๊ฒฐ๋œ๋‹ค.

BCR 1.1์€ ๊ฒฝ์ œ์  ์ž„๊ณ„์น˜๋ฅผ ์›ƒ๋„๋Š” ์ˆ˜์น˜์ง€๋งŒ ์ ˆ๋Œ€์ ์ธ ์ˆ˜์ต์„ฑ์ด ๋†’๋‹ค๊ณ  ํŒ๋‹จํ•˜๊ธฐ์—๋Š” ํ•œ๊ณ„๊ฐ€ ์žˆ๋‹ค. ๋”ฐ๋ผ์„œ ์‹ค์ œ ์šฉ์ง€ ํ™•๋ณด ๊ฐ€๋Šฅ์„ฑ ๋ฐ ๋Œ€์šฉ๋Ÿ‰ ์—ฐ๊ณ„ ์‹œ ๊ณ„ํ†ต ๋ณด๊ฐ• ๋น„์šฉ ๋“ฑ์„ ๊ณ ๋ คํ•œ ์ •๋ฐ€ ๋ถ„์„์„ ํ–ฅํ›„ ์—ฐ๊ตฌ ๊ณผ์ œ๋กœ ์ˆ˜ํ–‰ํ•  ์˜ˆ์ •์ด๋‹ค.

4. ๊ฒฐ ๋ก 

๋ณธ ์—ฐ๊ตฌ๋Š” ๋†์—…์šฉ ์ €์ˆ˜์ง€์˜ ์œ ํœด ์ž์›์„ ํ™œ์šฉํ•˜์—ฌ ๊ณ„ํ†ต ์•ˆ์ •์„ฑ๊ณผ ๊ฒฝ์ œ์„ฑ์„ ๋™์‹œ์— ํ™•๋ณดํ•  ์ˆ˜ ์žˆ๋Š” ํ•˜์ด๋ธŒ๋ฆฌ๋“œ ๋ฐœ์ „ ๋ชจ๋ธ์„ ์ œ์‹œํ•˜์˜€๋‹ค. ์‹œ๋ฎฌ๋ ˆ์ด์…˜์„ ํ†ตํ•ด ๊ณ„ํ†ต ์ฃผํŒŒ์ˆ˜ ์œ ์ง€ ๋Šฅ๋ ฅ์„ ์ž…์ฆํ•˜์˜€์œผ๋ฉฐ, ์ˆ˜์ƒ ํƒœ์–‘๊ด‘์˜ ์ตœ์  ์šฉ๋Ÿ‰ ์„ค๊ณ„๋ฅผ ํ†ตํ•ด ๊ฒฝ์ œ์  ํƒ€๋‹น์„ฑ ํ™•๋ณด๊ฐ€ ๊ฐ€๋Šฅํ•จ์„ ํ™•์ธํ•˜์˜€๋‹ค. ๋ณธ ๋ชจ๋ธ์€ ํ–ฅํ›„ ์‹ ์žฌ์ƒ์—๋„ˆ์ง€ ํ™•๋Œ€ ๋ฐ ํƒ„์†Œ ์ค‘๋ฆฝ ์‹คํ˜„์„ ์œ„ํ•œ ํšจ์œจ์ ์ธ ๋ถ„์‚ฐ ์ „์› ํ•ด๋ฒ•์œผ๋กœ ํ™œ์šฉ๋  ์ˆ˜ ์žˆ์„ ๊ฒƒ์ด๋‹ค.

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์ €์ž์†Œ๊ฐœ

์ด๋™์ฃผ (Dong-Ju Lee)
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He received the B.S., M.S. and Ph.D. degrees in electrical engineering from Chungnam national university, Daejon, Korea, in 1996, 1998 and 2021, respectively. From 1999 to 2010, he worked at R&D department of Ehwa Technologies Information as a chief research engineer for the development of commercial uninterruptible power supply system and military 400Hz power converter system. From 2010 to 2017, he worked at R&D department of Kukje Electric Co., Ltd. as a chief design engineer for the development of transformer-less uninterruptible power supply system and he is a chief technology officer for the developments of energy storage system since 2017. His research interests are in the areas of analysis and design of induction machine and development of power conversion system.

๊น€์ข…๊ฒธ (Jong-Gyeum Kim)
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Jong-Gyeum Kim received his B.S. degree in Electrical Engineering from Dong-A University, Busan, Korea, in 1984, and M.S. and Ph.D. in Electrical Engineering from Chungnam National University in 1991 and 1996, respectively. In 1987, he worked at KT, and from 1988 to 1996, he worked at K-water. He was a Visiting Professor at the University of Wisconsin-Madison from 2013 to 2014 and the University of Idaho from 2022 to 2023. He has been working at Kangwon National University since 1996. His research interests include the design and implementation of energy conversion system and power quality. He is a fellow member of the KIEE.